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(Added 09/30/04) The Genesis team is preparing to ship its samples of the sun from the mission's temporary cleanroom at the U.S. Army Proving Ground, Dugway, Utah, to NASA's Johnson Space Center, Houston.

"We have essentially completed the recovery and documentation process and now are in the business of preparing everything for transport," explained Eileen Stansbery, Johnson Space Center assistant director of astromaterials research and exploration science. "We still have a way to go before we can quantify our recovery of the solar sample. I can tell you we have come a long way from September 8, and things are looking very, very good."

A major milestone in the process was the recovery of the Genesis mission's four separate segments of the concentrator target. Designed to measure the isotopic ratios of oxygen and nitrogen, the segments contain within their structure the samples that are the mission's most important science goal.

"Retrieving the concentrator target was our number one priority," Stansbery said. "When I first saw three of the four target segments were intact, and the fourth was mostly intact, my heart leapt. Inside those segments are three years of the solar samples, which to the scientific community, means eons worth of history of the birth of our solar system. I saw those, and I knew we had just overcome a major hurdle."

Other milestones in the recovery process included the discovery that the gold foil collector was undamaged and in excellent condition. The gold foil, which is expected to contain almost a million billion atoms of solar wind, was considered the number two priority for science recovery. The polished aluminum collector was misshapen by the impact. However, it is intact and expected to also yield secrets about the sun. Another occurred when the cleanroom team disassembled the collector arrays. They revealed, among large amounts of useable array material, some almost whole sapphire and coated sapphire collectors and a metallic glass collector.

Packing solar samples for transport is a little different than packing a house-worth of belongings for a cross-country move. After the meticulous process of inspection and documentation, each segment of collector gets its own ID number, photograph and carrying case. The samples and shipping containers fill the space of about two full size refrigerators. The Genesis material will probably move to the Johnson Space Center within the next week.

"If you had told me September 8 that we would be ready to move Genesis samples to Houston within the month I would have replied, 'no way,'" remarked Genesis Project Manager Don Sweetnam of NASA's Jet Propulsion Laboratory, Pasadena, CA. "But here we are, with an opportunity to fulfill our major science objectives. It is a great day for Genesis, and I expect many more to come."

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-245.

(Added 09/30/04) The explosion of a massive star blazes with the light of 200 million suns in this NASA Hubble Space Telescope image. The arrow at top right points to the stellar blast, called a supernova. The supernova is so bright in this image that it easily could be mistaken for a foreground star in our Milky Way Galaxy. And yet, this supernova, called SN 2004dj, resides far beyond our galaxy. Its home is in the outskirts of NGC 2403, a galaxy located 11 million light-years from Earth. Although the supernova is far from Earth, it is the closest stellar explosion discovered in more than a decade.

The star that became SN 2004dj may have been about 15 times as massive as the sun and only about 14 million years old. A team of astronomers led by Jesus Maiz of the Space Telescope Science Institute discovered that the supernova was part of a compact cluster of stars known as Sandage 96, whose total mass is about 24,000 times the mass of the sun. Many such clusters - the blue regions - as well as looser associations of massive stars, can be seen in this image. The large number of massive stars in NGC 2403 leads to a high supernova rate. Two other supernovae have been seen in this galaxy during the past half-century.

The heart of NGC 2403 is the glowing region at lower left. Sprinkled across the region are pink areas of star birth. The many faint stars visible in the Hubble image belong to NGC 2403, but the handful of very bright stars in the image belong to our own Milky Way Galaxy and are only a few hundred to a few thousand light-years away. This image was taken on August 17, two weeks after an amateur astronomer discovered the supernova.

Japanese amateur astronomer Koichi Itagaki discovered the supernova on July 31, 2004, with a small telescope. Additional observations soon showed that it is a "Type II supernova," resulting from the explosion of a massive, hydrogen-rich star at the end of its life. The cataclysm probably occurred when the evolved star's central core, consisting of iron, suddenly collapsed to form an extremely dense object called a neutron star. The surrounding layers of gas bounced off the neutron star and also gained energy from the flood of neutrinos that may have been released, thereby violently expelling these layers.

This explosion is ejecting heavy chemical elements, generated by nuclear reactions inside the star, into the cosmos. Like other Type II supernovae, this exploding star is providing the raw material for future generations of stars and planets. Elements on Earth such as oxygen, calcium, iron, and gold came long ago from exploding stars such as this one.

Astronomers will continue to study SN 2004dj over the next few years, as it slowly fades from view, in order to gain a better understanding of how certain types of stars explode and what kinds of chemical elements they eject into space.

This color-composite photograph was obtained by combining images through several filters taken with the Wide Field Camera of the Advanced Camera for Surveys. The colors in the image highlight important features in the galaxy. Hot, young stars are blue. Older stars and dense dust lanes near the heart of the galaxy are red. The hydrogen-rich, star-forming regions are pink. The dense concentration of older stars in the galaxy's central bulge is yellow. In addition to the visible-light image shown here, ultraviolet images and spectra are being obtained with Hubble's Advanced Camera for Surveys. Astronomers are also using ground-based telescopes to study the supernova.

Adapted from the information on http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/23/.

(Added 09/26/04) As NASA's Spirit and Opportunity rovers resumed reliable contact with Earth after a period when Mars passed nearly behind the sun, the space agency extended funding for an additional six months of rover operations, as long as they keep working.

Both rovers successfully completed their primary three-month missions on the surface of Mars in April and have already added about five months of bonus exploration during the first extension of their missions.

"Spirit and Opportunity appear ready to continue their remarkable adventures," said Andrew Dantzler, solar system division director at NASA Headquarters, Washington. "We're taking advantage of that good news by adding more support for the teamwork here on Earth that's necessary for operating the rovers."

Neither rover drove during a 12-day period this month, while radio transmissions were unreliable because of the sun's position between the two planets. Daily planning and commanding of rover activities recommenced Monday for Opportunity and today for Spirit.

"It is a relief to get past this past couple of weeks," said Jim Erickson, project manager for both rovers at NASA's Jet Propulsion Laboratory, Pasadena, CA. "Not only were communications disrupted, but the rovers were also going through the worst part of Mars southern-hemisphere winter from a solar-energy standpoint."

"Although Spirit and Opportunity are well past warranty, they are showing few signs of wearing out," Erickson said. "We really don't know how long they will keep working, whether days or months. We will do our best to continue getting the maximum possible benefit from these great national resources."

Rover science team members will spend less time at JPL during the second mission extension. They are able to attend daily planning meetings by teleconferencing from their home institutions in several states and in Europe. "All 150 science team members and collaborators have been provided the tools to be able to participate remotely," explained JPL's Dr. John Callas, science manager for the rover project. Workstations researchers used at JPL are at their home institutions. Planning tools include video feeds, workstation display remote viewing, and audio conferencing.

Besides reducing costs, remote operations allow scientists to spend more time at home. "We get back to more normal lives, back to our families, and we still get to explore Mars every day," remarked Dr. Steve Squyres of Cornell University, Ithaca, NY, principal investigator.

Another change in operations is a shift from seven days per week to five days per week from October through December. This accommodates a temporary trim of about 20% in the project's engineering team to about 100 members. The rovers' reduced energy supply, during the rest of the martian winter, makes the inactive days valuable for recharging batteries. By January, the energy situation will have improved for the solar-powered rovers, provided they are still operating. The team size will rebound to support daily operations.

As Mars emerges from behind the sun, Spirit is partway up the west spur of highlands called the "Columbia Hills," a drive of more than 3 kilometers (2 miles) from its landing site. Opportunity is inside stadium-size "Endurance Crater," headed toward the base of a stack of exposed rock layers in "Burns Cliff," and a potential exit route on the crater's south side.

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-234.

(Added 09/26/04) Scientists examining Saturn's contorted F ring, which has baffled them since its discovery, have found one small body, possibly two, orbiting in the F ring region, and a ring of material associated with Saturn's moon Atlas.

A small object was discovered moving near the outside edge of the F ring, interior to the orbit of Saturn's moon Pandora. The object was seen by Dr. Carl Murray, imaging team member at Queen Mary, University of London, in images taken on June 21, 2004, just days before Cassini arrived at Saturn. "I noticed this barely detectable object skirting the outer part of the F ring. It was an incredible privilege to be the first person to spot it," he remarked. Murray's group at Queen Mary then calculated an orbit for the object.

Scientists cannot yet definitively say if the object is a moon or a temporary clump. If it is a moon, its diameter is estimated at four to five kilometers (two to three miles) and it is located 1,000 kilometers (620 miles) from the F ring, Saturn's outmost ring. It is at a distance of approximately 141,000 kilometers (86,000 miles) from the center of Saturn and within 300 kilometers (190 miles) of the orbit of the moon Pandora. The object has been provisionally named S/2004 S3.

Scientists are not sure if the object is alone. This is because of results from a search through other images that might capture the object to pin down its orbit. The search by Dr. Joseph Spitale, a planetary scientist working with team leader Dr. Carolyn Porco at the Space Science Institute in Boulder, CO, revealed something strange. Spitale said, "When I went to look for additional images of this object to refine its orbit, I found that about five hours after first being sighted, it seemed to be orbiting interior to the F ring," said Spitale. "If this is the same object then it has an orbit that crosses the F ring, which makes it a strange object." Because of the puzzling dynamical implications of having a body that crosses the ring, the inner object sighted by Spitale is presently considered a separate object with the temporary designation S/2004 S4. S4 is roughly the same size as S3.

Saturn's New Ring S/2004 1R In the process of examining the F ring region, Murray also detected a previously unknown ring, S/2004 1R, associated with Saturn's moon, Atlas. "We knew from Voyager that the region between the main rings and the F ring is dusty, but the role of the moons in this region was a mystery," said Murray. "It was while studying the F ring in these images that I discovered the faint ring of material. My immediate hunch was that it might be associated with the orbit of one of Saturn's moons, and after some calculation I identified Atlas as the prime suspect."

The ring is located 138,000 kilometers (86,000 miles) from the center of Saturn in the orbit of the moon Atlas, between the A ring and the F ring. The width of the ring is estimated at 300 kilometers (190 miles). The ring was first spotted in images taken after orbit insertion on July 1, 2004. There is no way of knowing yet if it extends all the way around the planet.

"We have planned many images to search the region between the A and F rings for diffuse material and new moons, which we have long expected to be there on the basis of the peculiar behavior of the F ring," said Porco. "Now we have found something but, as is usual for the F ring, what we see is perplexing."

Searches will continue for further detections of the newfound body or bodies seen in association with the F ring. If the two objects indeed turn out to be a single moon, it will bring the Saturn moon count to 34. The newfound ring adds to the growing number of narrow ringlets around Saturn.

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-222.

(Added 09/26/04) The Genesis mission was launched in August 2001 on a journey to capture samples from the storehouse of 99% of all the material in our solar system -- the Sun. The samples of solar wind particles, collected on ultra-pure wafers of gold, sapphire, silicon and diamond, were designed to be returned for analysis by Earth-bound scientists.

The Genesis sample return capsule entered Earth's atmosphere at 9:52:47 A.M. MDT on September 8 and entered the preplanned entry ellipse in the Utah Test and Training Range as predicted. However, the Genesis capsule, as a result of its parachute not deploying, impacted the ground at a speed of 311 km per hour (193 miles per hour). The impact occurred near Granite Peak on a remote portion of the range. No people or structures were anywhere near the area.

"We have the capsule," said Genesis project manager Don Sweetnam of NASA's Jet Propulsion Laboratory, Pasadena, CA. "It is on the ground. We have previously written procedures and tools at our disposal for such an event. We are beginning capsule recovery operations at this time."

By the time the capsule entered Earth's atmosphere, the flight crews tasked to capture Genesis were already in the air. Once it was confirmed the capsule touched down out on the range, the flight crews were guided toward the site to initiate a previously developed contingency plan. They landed close to the capsule and, per the plan, began to document the capsule and the area.

"For the velocity of the impact, I thought there was surprisingly little damage," said Roy Haggard of Vertigo Inc., Lake Elsinore, CA, who took part in the initial reconnaissance of the capsule. "I observed the capsule penetrated the soil about 50% of its diameter. The shell had been breached about three inches and I could see the science canister inside and that also appeared to have a small breach," he said.

The science canister from the Genesis mission was later moved into the cleanroom at the U.S. Army Dugway Proving Ground in Utah. First, a team of specialists plucked pieces of dirt and mud that had lodged in the canister after the mission’s sample return capsule landed at high speed in the Utah desert.

The Genesis team began examining the contents of the canister on Thursday morning. "This may result in snatching victory from the jaws of defeat," said Dr. Roger Wiens of the Los Alamos National Laboratory in New Mexico, a member of the Genesis science team, the next day. "We are very encouraged." Based on initial inspection, it is possible a repository of solar wind materials may have survived that will keep the science community busy for some time.

"We are pleased and encouraged by the preliminary inspection," said NASA Administrator Sean O'Keefe. "The outstanding design and sturdy construction of Genesis may yield the important scientific results we hoped for from the mission."

The mission's main priority is to measure oxygen isotopes to determine which of several theories is correct regarding the role of oxygen in the formation of the solar system. Scientists hope to determine this with isotopes collected in the four target segments of the solar wind concentrator carried by the Genesis spacecraft. "From our initial look, we can see that two of the four concentrator segments are in place, and all four may be intact," Wiens said.

The mission's second priority is to analyze nitrogen isotopes that will help us understand how the atmospheres of the planets in our solar system evolved. "These isotopes will be analyzed using gold foil, which we have also found intact," Wiens said. Other samples of solar winds are contained on hexagonal wafers.

Another type of collector material, foils contained on the canister's lid, were designed to collect other isotopes in the solar wind. It appears approximately three-fourths of these are recoverable, according to Dr. Dave Lindstrom, mission program scientist at NASA Headquarters. However, these foils have been exposed to elements of the Utah desert.

At present, the science canister that holds the majority of the mission's scientific samples is lying upside down - on its lid. Scientists are very methodically working their way "up" from the bottom portion of the canister by trimming away small portions of the canister's wall. The team continues to extract, from the interior of the science canister, small but potentially analyzable fragments of collector array material. One-half of a sapphire wafer was collected Tuesday - the biggest piece of collector array to date.

The condition of these segments will be better known over the next few days, after the canister's solar wind concentrator is extricated. At this time, it is believed that three of these segments are relatively intact and that the fourth may have sustained one or more fractures. There are no concrete plans regarding the shipping date of the Genesis capsule or its contents from Dugway to the Johnson Space Center in Houston. The team continues its meticulous work and believes that a significant repository of solar wind materials may have survived that will keep the science community busy for some time.

The Genesis team shipped its first scientific sample from the mission's specially constructed cleanroom at the U.S. Army Proving Ground in Dugway, Utah, on September 23 - 15 days after the craft landed in the desert. The sample, containing what are known as "lid foils," was attached to the interior lid of the Genesis sample return capsule.

"This is the first batch in what we are growing more confident will be many more scientifically valuable samples," said Genesis Project Manager Don Sweetnam of NASA's Jet Propulsion Laboratory, Pasadena, CA. "It appears that we have recovered about 75 to 80 percent of these lid foils. A great deal of credit has to go to the dedicated men and women of Genesis who continue to do very precise, detailed work out there in the Utah desert."

After the sample was shipped from Utah, it was received by Genesis co-investigator Nishiizumi Kunihiko from the University of California, Berkeley, Space Sciences Laboratory.

In addition to the lid foils, there was optimistic news about the collector array. Team members from JPL arrived in Utah on Monday with a special fixture to aid in handling the science canister's stack of four collector arrays. The stack was successfully removed as one piece. With the stack on the fixture, the team has begun the process of disassembling the arrays. Several large pieces of individual collector materials, including one completely intact hexagon, were recovered from the top array.

The Genesis cleanroom activities are focused on getting the materials ready for shipping. A date has not yet been selected for transporting the Genesis science canister and recovered collector materials from Dugway to NASA's Johnson Space Center in Houston. The team continues its meticulous work and believes that a significant repository of solar wind materials has survived that will keep the science community busy working on their science objectives.

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-219, http://www.jpl.nasa.gov/news/news.cfm?release=2004-221, http://www.jpl.nasa.gov/news/news.cfm?release=2004-225, http://www.jpl.nasa.gov/news/news.cfm?release=2004-228, http://www.jpl.nasa.gov/news/news.cfm?release=2004-231, and http://www.jpl.nasa.gov/news/news.cfm?release=2004-236.

(Added 09/26/04) A new class of planets beyond our solar system of unprecedented small size - about 10 to 20 times the size of Earth - has recently been detected. The planets make up a new class of Neptune-sized extrasolar planets. In addition, one of the new planets joins three others around the nearby star 55 Cancri to form the first known four-planet system.

The discoveries consist of two new planets. They were discovered by the world renowned planet-hunting team of Drs. Paul Butler and Geoffrey Marcy of the Carnegie Institute of Washington and University of California, Berkeley, respectively; and Barbara McArthur of the University of Texas, Austin. Both findings were peer-reviewed and accepted for future publication in the Astrophysical Journal. NASA and the National Science Foundation funded the research.

"These Neptune-sized planets prove that Jupiter-sized, gas giants aren't the only planets out there," Marcy said. Butler added, "We are beginning to see smaller and smaller planets. Earth-like planets are the next destination." Future NASA planet-hunting missions, including Kepler, the Space Interferometry Mission and the Terrestrial Planet Finder, will seek such Earth-like planets. Nearly 140 extrasolar planets have been discovered.

Both of the new planets stick very close to their parent stars, whipping around them in a matter of days. The first planet, discovered by Marcy and Butler, circles a small star called Gliese 436 about every 2.5 days at just a small fraction of the distance between Earth and the Sun, or 4.1 million kilometers (2.6 million miles). This planet is only the second known to orbit an M dwarf, a type of low-mass star 40% the size of our own sun. Gliese 436 is located in our galactic backyard, 30 light-years away in the constellation Leo.

The second planet, found by McArthur, speeds around 55 Cancri in just under three days, also at a fraction of the distance between Earth and the sun, at approximately 5.6 million kilometers (3.5 million miles). Three larger planets also revolve around the star every 15, 44 and 4,520 days, respectively. Marcy and Butler discovered the outermost of these in 2002. It is still the only known Jupiter-like gas giant to reside as far away from its star as our own Jupiter. The 55 Cancri is about 5 billion years old, a bit lighter than the sun, and is located 41 light-years away in the constellation Cancer. "55 Cancri is a premier laboratory for the study of planetary system formation and evolution," McArthur said.

Because the new planets are smaller than Jupiter, it is possible they are made of rock, or rock and ice, rather than gas. According to the scientists, the planets may have, like Earth, formed through gradual accumulation of rocky bodies. "A planet of Neptune's size may not have enough mass to hold onto gas, but at this point we don't know," Butler said.

Both discoveries were made using the "radial velocity" technique, in which a planet's gravitational tug is detected by the wobble it produces in the parent star. Butler, Marcy and collaborators, including Dr. Deborah Fischer of San Francisco State University and Dr. Steven Vogt of the University of California, Santa Cruz, discovered their "Neptune" after careful observation of 950 nearby stars with the W.M. Keck Observatory in Mauna Kea, Hawaii. They were able to spot such a relatively small planet, because the star it tugs on is small and more susceptible to wobbling.

McArthur and collaborators Drs. Michael Endl, William Cochran and Fritz Benedict of the University of Texas discovered their "Neptune" after obtaining over 100 observations of 55 Cancri from the Hobby- Eberly Telescope at McDonald Observatory in West Texas. Combining this data with past data from Marcy, Fischer and Butler from the Lick Observatory in California, and archival data from NASA's Hubble Space Telescope, the team was able to model the orbit of 55 Cancri's outer planet. This, in turn, allowed them to clearly see the orbits of the other three inner planets, including the new Neptune-sized one.

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-212.

(Added 09/26/04) NASA's Mars Odyssey orbiter begins working overtime today after completing a prime mission that discovered vast supplies of frozen water, ran a safety check for future astronauts, and mapped surface textures and minerals all over Mars, among other feats.

"Odyssey has accomplished all of its mission-success criteria," announced Dr. Philip Varghese, project manager for Odyssey at NASA's Jet Propulsion Laboratory, Pasadena, CA. The spacecraft has been examining Mars in detail since February 2002, more than a full Mars year of about 23 Earth months. NASA has approved an extended mission through September 2006.

"This extension gives us another martian year to build on what we have already learned," explained JPL's Dr. Jeff Plaut, project scientist for Odyssey. "One goal is to look for climate change. During the prime mission we tracked dramatic seasonal changes, such as the comings and goings of polar ice, clouds and dust storms. Now, we have begun watching for year-to-year differences at the same time of year."

The extension will also continue Odyssey's support for other Mars missions. About 85% of images and other data from NASA's twin Mars rovers, Spirit and Opportunity, have reached Earth via communications relay by Odyssey, which receives transmissions from both rovers every day. The orbiter helped analyze potential landing sites for the rovers and is doing the same for NASA's Phoenix mission, scheduled to land on Mars in 2008. Plans call for Odyssey to aid NASA's Mars Reconnaissance Orbiter, due to reach Mars in March 2006, by monitoring atmospheric conditions during months when the newly arrived orbiter uses calculated dips into the atmosphere to alter its orbit into the desired shape.

Odyssey was launched April 7, 2001, and used the same dips into the atmosphere, known as aerobraking, to shape its orbit during the initial months after it reached Mars on October 23, 2001. The spacecraft carries three research systems: a camera system made up of infrared and visible-light sensors; a spectrometer suite with a gamma ray spectrometer, a neutron spectrometer and a high-energy neutron detector; and a radiation environment detector.

Less than a month after the science mapping campaign began, the team announced a major discovery. The gamma ray and neutron instruments detected copious hydrogen just under Mars' surface in the planet's south polar region. Researchers interpret the hydrogen as frozen water - enough within about a meter (3 ft) of the surface, if the ice were melted, to fill Lake Michigan a couple times.

Here are a few of Odyssey's other important accomplishments so far:

As summer came to northern Mars and the north polar covering of frozen carbon dioxide shrank, Odyssey found abundant frozen water in the north, too.
Infrared mapping showed that a mineral called olivine is widespread. This indicated the environment has been quite dry, because water exposure alters olivine into other minerals.
Findings indicated the amount of frozen water in some relatively warm regions on Mars is too great to be in equilibrium with the atmosphere, suggesting that Mars may be going through a period of climate change. Features visible near small, young gullies in some Odyssey images may be slowly melting snowpacks left over from a martian ice age.
The first experiment sent to Mars specifically in preparation for human missions found that radiation levels around Mars, from solar flares and cosmic rays, are two to three times higher than around Earth.
Odyssey's camera system obtained the most detailed complete global maps of Mars ever, with daytime and nighttime infrared images at a resolution of 100 meters (328 feet).

"We've accomplished everything we set out to do, and more," said JPL's Robert Mase, Odyssey mission manager. Although an unusually powerful solar flare in October 2003 knocked out the radiation environment instrument, Odyssey is otherwise in excellent health. The spacecraft has enough fuel onboard to keep operating through this decade and the next at current consumption rates. The mission extension, with a budget of $35 million, essentially doubles the science payoff from Odyssey for less than one-eighth of the mission's original $297 million cost.

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-209.

(Added 09/26/04) Astronomers have used an x-ray image to make the first detailed study of the behavior of high-energy particles around a fast moving pulsar. The image, from NASA's Chandra X-ray Observatory, shows the shock wave created as a pulsar plows supersonically through interstellar space. These results will provide insight into theories for the production of powerful winds of matter and antimatter by pulsars.

Chandra's image of the glowing cloud, known as the Mouse, shows a stubby bright column of high-energy particles, about four light years in length, swept back by the pulsar's interaction with interstellar gas. The intense source at the head of the x-ray column is the pulsar, estimated to be moving through space at about 1.3 million miles per hour.

A cone-shaped cloud of radio-wave-emitting particles envelopes the x-ray column. The Mouse, AKA G359.23-0.82, was discovered in 1987 by radio astronomers using the National Science Foundation's Very Large Array in New Mexico. It gets its name from its appearance in radio images that show a compact snout, a bulbous body, and a remarkable long, narrow, tail that extends for about 55 light years.

"A few dozen pulsar wind nebulae are known, including the spectacular Crab Nebula, but none have the Mouse's combination of relatively young age and incredibly rapid motion through interstellar space," commented Bryan Gaensler of the Harvard-Smithsonian Center for Astrophysics and lead author of a paper on the Mouse. "We effectively are seeing a supersonic cosmic wind tunnel, in which we can study the effects of a pulsar's motion on its pulsar wind nebula, and test current theories."

Pulsars are known to be rapidly spinning, highly magnetized neutron stars - objects so dense that a mass equal to that of the Sun is packed into a diameter of about 12 miles. Their formation is associated with a Type II supernova, the collapse and subsequent explosion of a massive star. The origin of a pulsar's high velocity is not known, but many astrophysicists suspect that it is directly related to the explosive circumstances involved in the birth of the pulsar.

The rapid rotation and strong magnetic field of a pulsar can generate a wind of high-energy matter and antimatter particles that rush out at near the speed of light. These pulsar winds create large, magnetized bubbles of high-energy particles called pulsar wind nebulae. The x-ray and radio data on the Mouse have enabled Gaensler and his colleagues to constrain the properties of the ambient gas, to estimate the velocity of the pulsar, and to analyze the structure of the various shock waves created by the pulsar, the flow of particles away from the pulsar, and the magnetic field in the nebula.

Adapted from the information on http://chandra.harvard.edu/press/04_releases/press_092304.html.

(Added 09/26/04) The Hubble Heritage Team has released September's image of the planetary nebula NGC 6543, also known as the Cat's Eye Nebula. 3,000 light-years from us, the nebula lies in the constellation Draco; this image covers approximately 1.2 arcminutes across (1.2 light-years). The image is combined from data taken on May 4, 2002, for a total exposure time of 1.2 hours.

This image is a composite of three filters ([O III] (F502N), [O III] (F505N), and H-α+[N II] (F658N)), and it offers a view of what our sun might look like in 6 billion years.

Though the Cat's Eye Nebula was the first planetary nebula to be discovered, it is one of the most complex such nebulae seen in space. A planetary nebula forms when sun-like stars gently eject their outer gaseous layers that form bright nebulae with amazing and confounding shapes. In 1994, Hubble first revealed NGC 6543's surprisingly intricate structures, including concentric gas shells, jets of high-speed gas, and unusual shock-induced knots of gas.

As if the Cat's Eye itself isn't spectacular enough, this new image taken with Hubble's Advanced Camera for Surveys (ACS) reveals the full beauty of a bull's eye pattern of eleven or even more concentric rings, or shells, around the Cat's Eye. Each 'ring' is actually the edge of a spherical bubble seen projected onto the sky -- that's why it appears bright along its outer edge.

Observations suggest the star ejected its mass in a series of pulses at 1,500-year intervals. These convulsions created dust shells, each of which contain as much mass as all of the planets in our solar system combined (still only 1% of the sun's mass). These concentric shells make a layered, onion-skin structure around the dying star. The view from Hubble is like seeing an onion cut in half, where each skin layer is discernible.

Until recently, it was thought that such shells around planetary nebulae were a rare phenomenon. However, Romano Corradi (Isaac Newton Group of Telescopes, Spain) and collaborators, in a paper published in the European journal Astronomy and Astrophysics in April 2004, have instead shown that the formation of these rings is likely to be the rule rather than the exception.

The bull's-eye patterns seen around planetary nebulae come as a surprise to astronomers because they had no expectation of episodes of mass loss at the end of stellar lives that repeat every 1,500 years. Several explanations have been proposed, including cycles of magnetic activity somewhat similar to our own s0un's sunspot cycle, the action of companion stars orbiting around the dying star, and stellar pulsations. Another school of thought is that the material is ejected smoothly from the star, and the rings are created later on due to formation of waves in the outflowing material. It will take further observations and more theoretical studies to decide between these and other possible explanations.

Approximately 1,000 years ago, the pattern of mass loss suddenly changed, and the Cat's Eye Nebula started forming inside the dusty shells. It has been expanding ever since, as discernible in comparing Hubble images taken in 1994, 1997, 2000, and 2002. The puzzle is what caused this dramatic change? Many aspects of the process that leads a star to lose its gaseous envelope are still poorly known, and the study of planetary nebulae is one of the few ways to recover information about these last few thousand years in the life of a sun-like star.

Adapted from the information on http://heritage.stsci.edu/2004/27/.

(Added 08/24/04) Ten years and one month ago, between July 16-22, 1994, more than 20 fragments of the comet P/Shoemaker-Levy 9 collided with the planet Jupiter, all at about the same latitude, 45° S. Fragments were up to 1.2 miles (2 km) in diameter, and they sent plumes of hot gas into the atmosphere. Dark scars on Jupiter lasted for weeks.

Over a decade later, Jupiter's atmosphere still contains remnants of the comet impact, but scientists said last week that they are puzzled by how two substances have spread into different locations. In addition, the new study discovered two previously undetected chemicals in Jupiter's volumous gas layers.

The Cassini spacecraft, now orbiting Saturn, studied Jupiter as it flew by in 2000 and 2001. Shocks created by the impacts led to high-temperature chemical reactions that produced hydrogen cyanide, which remains in the air but has spread around in the last ten years. The comet also delivered carbon monoxide and water. Scientists believe that interaction with sunlight converted the carbon monoxide into carbon dioxide.

The hydrogen cyanide has diffused both north and sough, mixed by wave activity. Jupiter's many cloud bands carry material around the planet swiftly, but the bands do not mix easily. Not surprisingly then, the hydrogen cyanide is most abundant in a belt at the latitude where the comet was absorbed. 5° both north and south, its presence drops off sharply.

Surprisingly, the highest concentration of carbon monoxide has shifted away from the latitude of the impact. It is most prevalent poleward of 60° S and decreases abruptly, toward the equator, north of 50° S. Another smaller spike in its presence occurs at high northern latitudes, around 70-90° N.

"At high latitudes, precipitation of energetic oxygen ions probably occurs, associated with Jupiter's magnetically induced lights, known as aurora. These energetic ions could react with Jupiter's atmosphere to produce hydroxyl, which can oxidize carbon monoxide to produce carbon dioxide. We're scratching our heads, and we need to work through these, and perhaps other, scenarios," explained Flasar, who is principal investigator for Cassini's Composite Infrared Spectrometer.

The study, led by Virgil G. Kunde of the University of Maryland, was published Thursday in the online version of the journal Science.

The work also uncovered two new compounds, diacetylene and a so-called methyl radical, which are products of the breakup of methane by ultraviolet radiation from the sun. These were expected but had not been observed at Jupiter before.

So far as astronomers know, the more than 100 giant planets found outside our solar system might be something like Jupiter. Only one has had its atmosphere probed. Better knowledge of the substances in Jupiter, and how things move around, should help set the stage for grasping the formation and evolution of gaseous extrasolar planets, the researchers say.

"An understanding of the processes governing the composition and distribution of chemical species in Jupiter’s atmosphere is required to successfully understand the chemical composition of extrasolar planets," they write in the journal.

Adapted from the information on http://www.space.com/scienceastronomy/mystery_monday_040823.html.

(Added 08/23/04) This Hubble Space Telescope (HST) image shows an H II region in the Large Magellanic Cloud (LMC), named N44F. 160,000 light-years from us, the region of gas lies in the constellation Dorado; this image covers approximately 2 arcminutes across (98 light-years). The image is combined from data taken on March 25, 2000, for a total exposure time of 37 minutes. This image is a composite of two filters (H-α (F656N) and [S II] (F673N)).

In this unusual image, NASA's Hubble Space Telescope captures a rare view of the celestial equivalent of a geode -- a gas cavity carved by the stellar wind and intense ultraviolet radiation from a hot young star.

Real geodes are baseball-sized, hollow rocks that start out as bubbles in volcanic or sedimentary rock. Only when these inconspicuous round rocks are split in half do we get a chance to appreciate the inside of the rock cavity that is lined with crystals. In the case of Hubble's 35 light-year diameter "celestial geode," the transparency of its bubble-like cavity of interstellar gas and dust reveals the treasures of its interior.

The object, called N44F, is being inflated by a torrent of fast-moving particles (called a "stellar wind") from an exceptionally hot star once buried inside a cold dense cloud. Compared with our sun (which is losing mass through its solar wind), the central star in N44F is ejecting more than a 100 million times more mass per second. Also, the particles move much faster at about 4 million mph (7 million kph), as opposed to about 0.9 million mph (1.5 million kph) for our sun. Because the bright central star does not exist in empty space but is surrounded by an envelope of gas, the stellar wind collides with this gas, pushing it out, like a snowplow. This forms a bubble, whose striking structure is clearly visible in the crisp Hubble image.

The nebula N44F is one of a handful of known interstellar bubbles. Bubbles like these have been seen around evolved massive stars (Wolf-Rayet stars), and also around clusters of stars (where they are called "super-bubbles"). But they have rarely been viewed around isolated stars, as is the case here.

On closer inspection, N44F harbors additional surprises. The interior wall of its gaseous cavity is lined with several four- to eight-light-year-high finger-like columns of cool dust and gas. (The structure of these "columns" is similar to the Eagle Nebula's iconic "pillars of creation" photographed by Hubble a decade ago, and they are seen in a few other nebulae as well). The fingers are created by a blistering ultraviolet radiation from the central star. Like windsocks caught in a gale, they point in the direction of the energy flow. These pillars look small in this image only because they are much farther away from us than the Eagle Nebula's pillars.

N44F is part of the larger N44 complex, which is a large super-bubble, blown out by the combined action of stellar winds and multiple supernova explosions. N44 itself is roughly 1,000 light-years across. Several compact star-forming regions, including N44F, are found along the rim of the central super-bubble.

Adapted from the information on http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/26/.

(Added 08/23/04) A spectacular new image of Cassiopeia A from NASA's Chandra X-ray Observatory released today has nearly 200 times more data than the "First Light" Chandra image of this object made five years ago. The new image reveals clues that the initial explosion caused by the collapse of a massive star was far more complicated than suspected.

"Although this young supernova remnant has been intensely studied for years, this deep observation is the most detailed ever made of the remains of an exploded star," described Martin Laming of the Naval Research Laboratory in Washington, D.C. Laming is part of a team of scientists led by Una Hwang of the Goddard Space Flight Center in Greenbelt, MD. "It is a gold mine of data that astronomers will be panning through for years to come."

Cassiopea A in 3-Color X-Ray The one-million-second (about 11.5 days) observation of Cassiopeia A uncovered two large, opposed jet-like structures that extend to about 10 light years from the center of the remnant. Clouds of iron that have remained nearly pure for the approximately 340 years since the explosion were also detected. In the three-color image on the right, the jets are in the 4:00 and 10:00 positions.

"The presence of the bipolar jets suggests that jets could be more common in relatively normal supernova explosions than supposed by astronomers," explained Hwang.

X-ray spectra show that the jets are rich in silicon atoms and relatively poor in iron atoms. In contrast, fingers of almost pure iron gas extend in a direction nearly perpendicular to the jets. This iron was produced in the central, hottest regions of the star. The high silicon and low iron abundances in the jets indicate that massive, matter-dominated jets were not the immediate cause of the explosion, as these should have carried out large quantities of iron from the central regions of the star.

A working hypothesis is that the explosion produced high-speed jets similar to those in hypernovae that produce gamma-ray bursts, but in this case, with much lower energies. The explosion also left a faint neutron star at the center of the remnant. Unlike the rapidly rotating neutron stars in the Crab Nebula and Vela supernova remnants that are surrounded by dynamic magnetized clouds of electrons, this neutron star is quiet and faint, and pulsed radiation has not been detected from it. It may have a very strong magnetic field generated during the explosion that helped to accelerate the jets, and today resembles other strong-field neutron stars (AKA "magnetars") in lacking a nebula produced by strong winds.

Adapted from the information on http://chandra.harvard.edu/press/04_releases/press_082304.html; the research appeared in an upcoming issue of the Astrophysical Journal.

(Added 08/21/04) Scientists have discovered irregular lumps beneath the icy surface of Jupiter's largest moon, Ganymede. These irregular masses may be rock formations, supported by Ganymede's icy shell for billions of years. This discovery comes nearly a year after the orchestrated demise of NASA's Galileo spacecraft into Jupiter's atmosphere and more than seven years after the data were collected.

The findings have caused scientists to rethink what the interior of Ganymede might contain. The reported bulges reside in the interior, and there are no visible surface features associated with them. This tells scientists that the ice is probably strong enough, at least near the surface, to support these possible rock masses from sinking to the bottom of the ice for billions of years. But this anomaly could also be caused by piles of rock at the bottom of the ice.

"The anomalies could be large concentrations of rock at or underneath the ice surface. They could also be in a layer of mixed ice and rock below the surface with variations in the amount of rock," proposed Dr. John Anderson, a scientist and the paper's lead author at JPL. "If there is a liquid water ocean inside Ganymede's outer ice layer there might be variations in its depth with piles of rock at the ocean bottom. There could be topographic variations in a hidden rocky surface underlying a deep outer icy shell. There are many possibilities, and we need to do more studies."

Ganymede's Mass Anomalies from Galileo Measurements Dr. Gerald Schubert, co-author at UCLA, explained "Although we don't yet have anything definitive about the depth at this point, we did not expect Ganymede's ice shell to be strong enough to support these lumpy mass concentrations. Thus, we expect that the irregularities would be close to the surface where the ice is coldest and strongest, or at the bottom of the thick ice shell resting on the underlying rock. It would really be a surprise if these masses were deep and in the middle of the ice shell."

Ganymede has three main layers: A sphere of metallic iron at the center (the core), a spherical shell of rock (mantle) surrounding the core, and a spherical shell of mostly ice surrounding the rock shell and the core. The ice shell on the outside is very thick, maybe 800 km (497 miles) thick. The surface is the very top of the ice shell. Though it is mostly ice, the ice shell might contain some rock mixed in. Scientists believe there must be a fair amount of rock in the ice near the surface. Variations in this amount of rock may be the source of these possible rock formations.

Scientists stumbled on the results by studying Doppler measurements of Ganymede's gravity field during Galileo's second flyby of the moon in 1996. Scientists were measuring the effect of the moon's gravity on the spacecraft as it flew by. They found unexpected variations.

"Believe it or not, it took us this long to straighten out the anomaly question, mostly because we were analyzing all 31 close flybys for all four of Jupiter's large moons," said Anderson. "In the end, we concluded that there is only one flyby, the second flyby of Ganymede, where mass anomalies are evident."

Scientists have seen mass concentration anomalies on one other moon before, Earth's, during the first lunar orbiter missions in the 1960s. The lunar mass concentrations during the Apollo moon mission era were due to lava in flat basins. However, scientists cannot draw any similarities between these mass concentrations and what they see at Ganymede.

"The fact that these mass anomalies can be detected with just flybys is significant for future missions," said Dr. Torrence Johnson, former Galileo project scientist. "With this type of information you could make detailed gravity and altitude maps that allow us to actually map structures within the ice crust or on the rocky surface. Knowing more about the interior of Ganymede raises the level of importance of looking for gravity anomalies around Jupiter's moons and gives us something to look for. This might be something NASA's proposed Jupiter Icy Moons Orbiter Mission could probe into deeper."

The paper was co-authored by Dr. Robert A. Jacobson and Eunice L. Lau of JPL, with Dr. William B. Moore and Jennifer L. Palguta of UCLA.

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-200; the research appeared in the August 13 issue of the journal Science.

(Added 08/21/04) The Cassini spacecraft has uncovered two new moons, and they may be the smallest bodies so far seen around the ringed planet.

The moons are approximately 3 km (2 miles) and 4 km (2.5 miles) across -- smaller than the city of Boulder, CO. The moons, located 194,000 km (120,000 miles) and 211,000 km (131,000 miles) from the planet's center, are between the orbits of two other saturnian moons, Mimas and Enceladus. They are provisionally named S/2004 S1 and S/2004 S2. One of them, S/2004 S1, may be an object spotted in a single image taken by NASA's Voyager spacecraft 23 years ago, called at that time S/1981 S14.

"One of our major objectives in returning to Saturn was to survey the entire system for new bodies," remarked Dr. Carolyn Porco, imaging team leader, Space Science Institute, Boulder, CO. Porco planned the imaging sequences. "So, it's really gratifying to know that among all the other fantastic discoveries we will make over the next four years, we can now add the confirmation of two new moons, skipping unnoticed around Saturn for billions of years until just now."

The moons were first seen by Dr. Sebastien Charnoz, a planetary dynamicist working with Dr. Andre Brahic, imaging team member at the University of Paris. "Discovering these faint satellites was an exciting experience, especially the feeling of being the first person to see a new body of our solar system," said Charnoz. "I had looked for such objects for weeks while at my office in Paris, but it was only once on holiday, using my laptop, that my code eventually detected them. This tells me I should take more holidays."

The smallest previously known moons around Saturn are about 20 km (12 miles) across. Scientists expected that moons as small as S/2004 S1 and S/2004 S2 might be found within gaps in the rings and perhaps near the F ring, so they were surprised these small bodies are between two major moons. Small comets careening around the outer solar system would be expected to collide with small moons and break them to bits. The fact that these moons exist where they do might provide limits on the number of small comets in the outer solar system, a quantity essential for understanding the Kuiper Belt of comets beyond Neptune, and the cratering histories of the moons of the giant planets.

"A comet striking an inner moon of Saturn moves many times faster than a speeding bullet," remarked Dr. Luke Dones, an imaging team member from the Southwest Research Institute in Boulder, CO. "If small, house-sized comets are common, these moons should have been blown apart many times by cometary impacts during the history of the solar system. The disrupted moon would form a ring, and then most of the material would eventually gather back together into a moon. However, if small comets are rare, as they seem to be in the Jupiter system, the new moons might have survived since the early days of the solar system."

Moons surrounding the giant planets generally are not found where they originally formed because tidal forces from the planet can cause them to drift from their original locations. In drifting, they may sweep through locations where other moons disturb them, making their orbits eccentric or inclined relative to the planet's equator. One of the new moons might have undergone such an evolution.

Upcoming imaging sequences will scour the gaps in Saturn's rings in search of moons believed to be there. Meanwhile, Cassini scientists are eager to get a closer look, if at all possible, at their new finds. Porco said, "We are at this very moment looking to see what the best times are for re-targeting. Hopefully, we haven't seen the last of them."

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-202.

(Added 08/21/04) Now that NASA's Mars Exploration Rover Spirit is finally examining bedrock in the "Columbia Hills," it is finding evidence that water thoroughly altered some rocks in Mars' Gusev Crater. Spirit and its twin, Opportunity, completed successful three-month primary missions on Mars in April and are returning bonus results during extended missions. They remain in good health though are beginning to show signs of wear.

On Opportunity, a tool for exposing the insides of rocks stopped working Sunday, but engineers are optimistic that the most likely diagnosis is a problem that can be fixed soon. "It looks like there's a pebble trapped between the cutting heads of the rock abrasion tool," explained Chris Salvo, rover mission manager at NASA's Jet Propulsion Laboratory, Pasadena, CA. "We think we can treat it by turning the heads in reverse, but we are still evaluating the best approach to remedy the situation. There are several options available to us."

Mars Exploration Rover (MER) Spirit - Longhorn rock outcrop with Gusev Crater in Background Opportunity originally landed right beside exposed bedrock and promptly found evidence there for an ancient body of saltwater. On the other hand, it took Spirit half a year of driving across a martian plain to reach bedrock in Gusev Crater. Now, Spirit's initial inspection of an outcrop called "Clovis" on a hill about 9 m (30 ft) above the plain suggests that water may once have been active at Gusev.

"We have evidence that interaction with liquid water changed the composition of this rock," remarked Dr. Steve Squyres of Cornell University, Ithaca, NY, principal investigator for the science instruments on both rovers. "This is different from the rocks out on the plain, where we saw coatings and veins apparently due to effects of a small amount of water. Here, we have a more thorough, deeper alteration, suggesting much more water. To really understand the conditions that altered Clovis, we'd like to know what it was like before the alteration. We have the 'after.' Now we want the 'before.' If we're lucky, there may be rocks nearby that will give us that."

Mars Exploration Rover (MER) Opportunity - Two Types of Pebblesin Endurance Crater Dr. Doug Ming, a rover science team member from NASA's Johnson Space Center, Houston, said indications of water affecting Clovis come from analyzing the rock's surface and interior with Spirit's alpha particle X-ray spectrometer and finding relatively high levels of bromine, sulfur and chlorine inside the rock. He said, "This is also a very soft rock, not like the basaltic rocks seen back on the plains of Gusev Crater. It appears to be highly altered."

Opportunity has completed a transect through layers of rock exposed in the southern inner slope of stadium-sized "Endurance Crater." The rocks examined range from outcrops near the rim down through progressively older and older layers to the lowest accessible outcrop, called "Axel Heiberg" after a Canadian Arctic island. "We found different compositions in different layers," said Dr. Ralf Gellert, of Max-Planck-Institut fur Chemie, Mainz, Germany. Chlorine concentration increased up to threefold in middle layers. Magnesium and sulfur declined nearly in parallel with each other in older layers, suggesting those two elements may have been dissolved and removed by water.

Small, gray stone spheres nicknamed "blueberries" are plentiful in Endurance - just as they were at Opportunity's smaller landing-site crater, "Eagle." Pictures from the rover's microscopic imager show a new variation on the blueberries throughout a reddish-tan slab called "Bylot" in the Axel Heiberg outcrop. "They're rougher textured, they vary more in size, and they're the color of the rock, instead of gray," said Zoe Learner, a science team collaborator from Cornell. "We've noticed that in some cases where these are eroding, you can see a regular blueberry or a berry fragment inside." One possibility is that a water-related process has added a coarser outer layer to the blueberries, she said, adding, "It's still really a mystery."

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-204.

(Added 08/21/04) The Milky Way Galaxy currently holds well over 100 globular clusters, but it once possessed many more. According to the hierarchical theory of galaxy formation, galaxies have grown larger over time by consuming smaller dwarf galaxies and star clusters. Sometimes, it seems that the unfortunate prey is not swallowed whole but instead is munched like a peach, stripped of its outer layers to leave behind only the pit.

New research by Paul Martini (Harvard-Smithsonian Center for Astrophysics) and Luis Ho (Observatories of the Carnegie Institution of Washington) shows that some globular clusters may be remnants of dwarf galaxies that were stripped of their outer stars, leaving only the galaxy's nucleus behind.

Their findings hint at an important yet puzzling connection between the largest globular clusters and the smallest dwarf galaxies. "Star clusters and galaxies are quite different from a structural standpoint - star clusters are much more centrally concentrated, for example - and so the mechanisms that form them must be quite different. Identification of star clusters in the same mass range as galaxies is a very important step toward understanding how both types of objects form," explained Martini.

For their investigation, the team studied 14 globular clusters in the large elliptical galaxy Centaurus A (NGC 5128) using the 6.5-m diameter Magellan Clay telescope at Carnegie's Las Campanas Observatory, Chile. The clusters were selected for their brightness, and since brighter clusters tend to contain more stars and more mass, they were expected to be massive. Yet their results were surprising, showing that the globular clusters of Centaurus A are much more massive than most globulars in the Local Group of galaxies (which includes the Milky Way and Andromeda Galaxies).

"The essence of our findings is that these 14 globulars are 10 times more massive than the smaller globulars in our neighborhood, and whatever process makes them can produce some really huge objects - they begin to overlap with the smallest galaxies," says Martini.

Martini also pointed out the recent discovery of a suspected intermediate-mass black hole in the Andromeda Galaxy globular cluster known as G1, which offers further evidence linking globular clusters to dwarf galaxies. The presence of a moderate-sized black hole is more understandable if it once occupied the center of a dwarf galaxy - a galaxy that lost its outer stars to the pull of Andromeda, leaving it only a shadow of its former self.

Ho, a co-discoverer of the intermediate-mass black hole in G1, adds, "One of the most surprising findings is that the black hole in G1 obeys the same tight correlation between black hole mass and host galaxy mass that has been well established for supermassive black holes in the centers of big galaxies. This puzzling result is more understandable if G1 was once the nucleus of a larger galaxy. A very interesting question is whether some of the massive clusters in Centaurus A also contain central black holes."

Although most of our Galaxy's globular clusters are much smaller than those of Centaurus A, the largest Milky Way globulars (such as the omega Centauri star cluster) rival those of the elliptical galaxy. The similarities between massive globulars in both galaxies may point to similar formation mechanisms. Future studies of these most massive globular clusters will explore connections between the formation processes for star clusters and galaxies.

Centaurus A is located approximately 12.5 million light-years away. It is about 65,000 light-years across and is more massive than the Milky Way and Andromeda galaxies put together. Centaurus A possesses a total of about 2000 globular clusters - more than all of the galaxies in the Local Group combined. Recent Spitzer Space Telescope observations of Centaurus A uncovered evidence that it merged with a spiral galaxy about 200 million years ago.

Adapted from the information on http://cfa-www.harvard.edu/press/pr0426.html; the research appeared in the July 20 issue of the Astrophysical Journal.

(Added 08/21/04) The Hubble Heritage Team has released August's image of the spiral galaxy NGC 3949. 50 million light-years from us, the galaxy lies in the constellation Ursa Major; this image covers approximately 2 arcminutes across (30,000 light-years). The image is combined from data taken on October 1, 2001, for a total exposure time of 16 minutes.

This image is a composite of three filters (B (F450W), V (F606W), and I (F814)), and it offers a view of what our galaxy might look like if we were to somehow get an image from millions of light-years outside of it.

Because we are embedded within our galaxy, it is very difficult to study many of its features. The next-best thing is to look at other galaxies that we believe resemble ours, such as NGC 3949. The galaxy has a blue disk of young stars peppered with bright pink star birth regions. In contrast to the young, blue disk, the bright central bulge is comprised of mostly older, redder stars.

NGC 3949 is a member of a loose cluster of over 70 galaxies located in the direction of the Big Dipper. It is one of the larger galaxies in that cluster.

Adapted from the information on http://heritage.stsci.edu/2004/25/.

(Added 07/31/04) The largest moon of Saturn, Titan, has the thickest atmosphere of any moon in the solar system. Cassini's cameras are starting to reveal some of the intricate structure of this alien atmosphere.

The image on the left shows Titan's atmosphere on July 3, 2004, one day after Cassini's first flyby of the moon. The image was taken in an ultraviolet filter, and it has been falsely colored to show the planet at is appears in visible light. The UV filter shows a high stratospheric haze along with a detached layer.

The lower layer is stratospheric haze. The atmosphere undergoes photochemical processes to form the hazes. Images like this reveal some of the key steps to the formation and evolution of Titan's haze. The process is thought to begin in the high atmosphere, at altitudes above 400 km (250 miles), where UV light breaks down methane and nitrogen molecules. The products are believed to react to form more complex organic molecules containing carbon, hydrogen, and nitrogen that can then combine to form the very small particles seen as haze.

The two distinct layers of atmospheric haze have been brightened and falsely colored violet to enhance their visibility. It is not currently understood why there are two separate haze layers. The bottom of the detached layer is a few hundred kilometers above the surface of the planet, and it is approximately 120 km (75 miles) thick.

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-187.

(Added 07/31/04) With 31 known moons, Saturn has the second-most known for a single planet in the solar system. One of them is Iapetus, and since its discovery in 1672, it has been known to have a split personality with one side very bright and the other very dark. New Cassini images reveal more information on this unique moon.

Iapetus was discovered by the Italian-French astronomer Jean Dominique Cassini in 1672. He correctly deduced that the trailing hemisphere is composed of highly reflective material while the leading hemisphere is much darker. Modern measurements show that the trailing hemisphere reflects about 50% of the light that hits it, while the leading is much darker and redder, and it only reflects about 3-4% of the light that hits it.

The moon is about 1,436 km (892 miles) wide. The Cassini image (right) was taken in visible light with the narrow angle camera on July 3, 2004, from a distance of about 3 million km (1.8 million miles) from Iapetus. The brightness variations shown are not due to shadowing nor image processing - they are real. Cassini will continue to image Iapetus and conduct two close encounters, one of them from a distance of only 1,000 km (622 miles).

The patterning of the light and dark is reversed from the other Saturnian and Jovian moons, which tend to be brighter on their leading rather than trailing hemispheres. Voyager images revealed this feature, which was very surprising at the time.

One scenario for the outside deposition of material has the dark particles being ejected from Saturn's moon Phoebe and drifting inwards to coat Iapetus. One observation lending support for an internal origin, however, is the concentration of material on crater floors, which is suggestive of something filling in the craters.

Besides its coloring, Iapetus is odd in other respects. It is in a moderately inclined orbit, taking it far above and bellow the plane in which the rings and most of the moons orbit. It is much less dense than many of the other satellites, which suggests a higher fraction of ice or possibly methane or ammonia in its interior.

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-182.

(Added 07/31/04) Until now, astronomers had only directly measured the mass of one star - the sun. Now, a small, red star, located about 1,800 light-years away, has been directly weighed, adding an important calibration to understanding stellar evolution.

Previously, astronomers could only determine the masses of stars that are members of binary systems by using Newton's laws of gravity and Kepler's Laws. The new measurement takes its technique from Einstein's theory of relativity, combined with a large-scale program using ground-based telescopes, and the exquisite resolution of NASA's Hubble Space Telescope.

The star first came into the limelight when it passed directly in front of a much more distant star in 1993, producing a phenomenon called gravitational microlensing. Microlensing - predicted by Einstein's theory of general relativity, occurs because of the warping of space around a massive object like a star. The warped space acts like a lens, focusing and magnifying the light of the background star, causing it to brighten suddenly, as seen by us. There have been several surveys over the past few years to search for these microlensing events.

In most cases, the transiting star is much fainter than the background star. But the light from one of the events discovered in 1993, dubbed MACHO-LMC-5, didn't just brighten. Changes in its color suggested that the background star and the lensing star were of similar brightness. This raised the possibility that the two stars could be observed separately, if astronomers waited a few years to give the foreground star time to move away from its perfect alignment with the background star.

Ground-based telescopes, however, could not resolve the stars as two separate objects. So, astronomers turned to Hubble's Wide Field Planetary Camera 2 in 1999, and later, in 2002 and 2003, to Hubble's Advanced Camera for Surveys. These observations succeeded in showing the two stars separately.

Seeing the two stars allowed astronomers to calculate the foreground star's distance from Earth, using a method called parallax. Due to the motion of the Earth around the Sun, the position of a nearby star will appear to shift relative to stars farther away. By measuring this shift, astronomers can triangulate the distance to the star. Surveyors use a similar method to measure distances on Earth. The distance derived in this way also agrees with the distance inferred from details of the brightness variations in 1993, based on subtle changes resulting from the motion of the Earth during the lensing event.

Once the distance to the lensing star was known, and since the distance to the Large Magellanic Cloud, where the background star is located, is also known, astronomers could calculate the only remaining unknown in the equation for microlensing, which is the mass of the foreground star. Its mass turns out to be one-tenth the mass of our own sun. Although a low mass of about this amount was expected based on the faintness of the red star, astronomers are nevertheless excited by this first application of a new method for measuring stellar masses. They hope to apply it many times in the future, by using the planned Space Interferometry Mission satellite to observe many more microlensing events.

Adapted from the information on http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/24/text/.

(Added 07/31/04) On May 12, 2002, a group of astronomers were observing a supernova in a distant galaxy with a spectrograph on the European Southern Observatory's Very Large Telescope. Across the field fell a meteor, and the spectrograph captured a very high-resolution spectrum of it as it fell through Earth's atmosphere, making it a reference for this field of research.

From the spectrum, the temperature of the meteor trail was estimated to be about 4600 °C. The serendipitous spectrum reveals the tell-tale meteor emissions of oxygen and nitrogen atoms and nitrogen molecules. The VLT spectrum was the first to reveal the far red range where carbon emission lines are predicted; the absence of the lines puts constraints on the role of atmospheric chemistry when life started on earth.

Because the VLT is tuned to observe objects far out in space, it focuses at infinity. The meteor, being only 100 km above the telescope, therefore appears out of focus in the field of view. This is the first spectrum to be obtained by a large telescope with a modern spectrograph.

Adapted from the information on http://www.eso.org/outreach/press-rel/pr-2004/pr-19-04.html.

(Added 07/31/04) McNeil's Nebula, a small nebula approximately 1300 light-years away in the Orion Nebula, was discovered by McNeil, an amateur astronomer from Paducah, KY, in January 2004 with a 3-inch (7.5-cm) telescope. The area had recently been surveyed in both optical and infrared light in late 2003, and also in November 2002 in x-rays. The timing of the nebula's luminescence and the recent surveys of the area have allowed unprecedented science to be conducted.

Recent observations with NASA's Chandra X-ray Observatory have captured an x-ray outburst from a young star, and they reveal a probable scenario for the intermittent brightening of the nebula. It appears that the interaction between the young star's magnetic field and an orbiting disk of gas can cause dramatic, episodic increases in the light from the star and disk, illuminating the surrounding gas.

Chandra's observations, just after the optical burst that allowed the nebula's discovery, show that the source has brightened by a factor of 50 compared with the observations in November 2002. The visible-light eruption provides evidence that the cause of the x-ray outburst is the sudden in fall of matter onto the star's surface from an orbiting disk of gas.

In general, the coupling of the magnetic field of a star and the magnetic field of its circumstellar disk regulates the inflow of gas from the disk onto the star. This slow, steady inflow suddenly can become much more rapid if a large amount of gas accumulates in the disk, and the disk and the star are rotating at different rates. The differing rotation rates would twist and shear the magnetic field, storing up energy. This energy is eventually released in an energetic, x-ray producing outburst as the magnetic field violently rearranges back to a more stable state. During this period, a large amount of gas can fall onto the star, producing the observed optical and infrared outburst.

A new buildup of gas in the disk could lead to a new outburst in the future. Such a scenario may explain why the brightness of McNeil's Nebula appears to vary with time. It is faintly present in surveys of this region of Orion in images taken in the 1960s, but absent from images taken in the 1950s and 1990s.

Adapted from the information on http://chandra.harvard.edu/press/04_releases/press_072204.html; the research appeared in the July 22 issue of the journal Nature.

(Added 07/10/04) Due to the length of this article, it has been divided into three sections: Cassini Makes Orbit, Saturn's Rings as Never Before, and Saturn's Moon - Titan.

Cassini Makes Orbit Saturn from Cassini

The international Cassini-Huygens mission has successfully entered orbit around Saturn. At 9:12 p.m. PDT on Wednesday, June 30, flight controllers received confirmation that Cassini had completed the engine burn needed to place the spacecraft into the correct orbit. This begins a four-year study of the giant planet, its majestic rings and 31 known moons.

"This is a tribute to the team at NASA and our partners at the European Space Agency and the Italian Space Agency, to accomplish this feat taking place 934 million miles [1.5 billion km] away from Earth," proclaimed Dr. Ed Weiler, associate administrator for space science at NASA Headquarters, Washington, D.C. "What Cassini-Huygens will reveal during its tour of Saturn and its many moons, including Titan, will astonish scientists and the public. Everyone is invited to come along for the ride and see all this as it is happening. It truly is a voyage of discovery."

Members of the Cassini-Huygens mission at NASA's Jet Propulsion Laboratory, Pasadena, CA, broke into cheers and high-fives as NASA's Deep Space Network confirmed receipt of the signal indicating successful entry into orbit. "We didn't expect anything less and couldn't have asked for anything more from the spacecraft and the team," remarked Robert T. Mitchell, program manager for the Cassini-Huygens mission at JPL. "This speaks volumes to the tremendous team that made it all happen."

Dr. Charles Elachi, JPL director and team leader on the radar instrument onboard Cassini, said, "It feels awfully good to be in orbit around the lord of the rings. This is the result of 22 years of effort, of commitment, of ingenuity, and that's what exploration is all about."

The mission will face another dramatic challenge in December, when the spacecraft will release the piggybacked Huygens probe – provided by the European Space Agency – which will plunge through the hazy atmosphere of Saturn's largest moon, Titan. "This was America's night. This was NASA doing it right," said Dr. David Southwood, director of scientific programs for the European Space Agency. "They really gave those of us in Europe a challenge. We've got six months to go until we land on Titan. We're just praying that everything will go as well."

Julie Webster, Cassini-Huygens spacecraft team chief, said, "The spacecraft has been an incredible joy to fly. We stand on the shoulders of people who had 40 years of experience building and designing spacecraft."

Cassini traveled nearly 3.5 billion kilometers (2.2 billion miles) to reach Saturn after its launch from Cape Canaveral Air Force Station, FL, on October 15, 1997. During Cassini's four-year mission, it will execute 52 close encounters with seven of Saturn's 31 known moons.

Besides the camera that has sent back many remarkable images (several shown below), other instruments have also been busy collecting data. The magnetospheric imaging instrument took the first image of Saturn's magnetosphere. "With Voyager we inferred what it looked like, in the same way that a blind man feels an elephant. Now we can see the elephant," said Dr. Tom Krimigis of Johns Hopkins Applied Physics Laboratory, Laurel, MD, principal investigator for the magnetospheric imaging instrument. The magnetosphere is a bubble of energetic particles around the planet shaped by Saturn's magnetic field and surrounded by the solar wind of particles speeding outward from the Sun.

"During approach to Saturn, Cassini was greeted at the gate," said Dr. Bill Kurth, deputy principal investigator for the radio and plasma wave science instrument onboard Cassini. "The bow shock where the solar wind piles into the planet's magnetosphere was encountered earlier than expected. It was as if Saturn's county line had been redrawn, and that was a surprise." Cassini first crossed the bow shock about 3 million kilometers (1.9 million miles) from Saturn, which is about 50 percent farther from the planet than had been detected by the Pioneer, Voyager 1 and Voyager 2 spacecraft that flew past Saturn in 1979, 1980 and 1981.

The location of the bow shock varies with how hard the solar wind is blowing, Kurth explained. As the magnetosphere repeatedly expanded and contracted while Cassini was approaching Saturn, the spacecraft crossed the bow shock seven times.

Cassini's examination of Saturn's atmosphere began while the spacecraft was still approaching the planet. Winds on Saturn near the equator decrease dramatically with altitude above the cloud tops. The winds fall off by as much 140 meters per sec (300 mph) over an altitude range of 300 kilometers (200 miles) in the upper stratosphere. This is the first time winds have been measured at altitudes so high in Saturn's atmosphere.

"We are finally defining the wind field in three dimensions, and it is very complex," said Dr. Michael Flasar of NASA Goddard Space Flight Center, Greenbelt, MD, principal investigator for Cassini's composite infrared spectrometer. "Temperature maps obtained now that Cassini is orbiting Saturn are expected to show more detail, helping us to unravel the riddles of Saturn's winds above the cloud tops."

Saturn's Rings as Never Before

Saturn's Rings in UV The first pictures taken by the Cassini spacecraft after it began orbiting Saturn show breathtaking detail of Saturn's rings, and other science measurements reveal that Saturn's magnetic field pulsed in size as Cassini approached the planet.

"For years, we've dreamed about getting pictures like this. After all the planning, waiting and worrying, just seeing these first images makes it all worthwhile," said Dr. Charles Elachi, Cassini radar team leader and director of NASA's Jet Propulsion Laboratory, Pasadena, CA. "We're eager to share these new views and the exciting discoveries ahead with people around the world."

The narrow angle camera on Cassini took 61 images soon after the main engine burn that put Cassini into orbit on Wednesday night. The spacecraft was hurtling at 15 km/s (about 34,000 mph), so only pieces of the rings were targeted. "We won't see the whole puzzle, only pieces, but what we are seeing is dramatic," said Dr. Carolyn Porco, Cassini imaging team leader, Space Science Institute, Boulder, CO. "The images are mind-boggling, just mind-boggling. I've been working on this mission for 14 years and I shouldn't be surprised, but it is remarkable how startling it is to see these images for the first time."

Some images show patterned density waves in the rings, resembling stripes of varying width. Another shows a ring's scalloped edge. "We do not see individual particles but a collection of particles, like a traffic jam on a highway," Porco explained. "We see a bunch of particles together, then it clears up, then there's traffic again."

Saturn's Rings' Composition One early science result intriguing scientists concerns Saturn’s Cassini Division, the large gap between the A and B rings. While Saturn’s rings are almost exclusively composed of water ice, new findings show the Cassini Division contains relatively more "dirt" than ice. Further, the particles between the rings seem remarkably similar to the dark material that scientists saw on Saturn’s moon, Phoebe. These dark particles refuel the theory that the rings might be the remnants of a moon. The F ring was also found to contain more dirt.

Another instrument on Cassini has detected large quantities of oxygen at the edge of the rings. Scientists are still trying to understand these results, but they think the oxygen may be left over from a collision that occurred as recently as January of this year.

"In just two days, our ideas about the rings have been expanded tremendously," remarked Dr. Linda Spilker, of NASA's Jet Propulsion Laboratory, Pasadena, CA, deputy project scientist for the Cassini-Huygens mission. "The Phoebe-like material is a big surprise. What puzzles us is that the A and B rings are so clean and the Cassini Division between them appears so dirty." The visual and infrared mapping spectrometer onboard Cassini revealed the dirt mixed with the ice in the Cassini Division and in other small gaps in the rings, as well as in the F ring.

"The surprising fingerprint in the data is that the dirt appears similar to what we saw at Phoebe. In the next several months we will be looking for the origin of this material," said Dr. Roger Clark, of the U.S. Geological Survey, Denver, CO, and a member of the Cassini science team. Cassini's ultraviolet imaging instrument detected the sudden and surprising increase in the amount of atomic oxygen at the edge of the rings. The finding leads scientists to hypothesize that something may have collided with the main rings, producing the excess oxygen.

Saturn's Rings' Size Dr. Donald Shemansky of the University of Southern California, Los Angeles, co-investigator for Cassini's ultraviolet imaging spectrograph instrument, said, "What is surprising is the evidence of a strong, sudden event during the observation period causing substantial variation in the oxygen distribution and abundance." Although atomic oxygen has not been previously observed, its presence is not a surprise because hydroxyl was discovered earlier from Hubble Space Telescope observations, and these chemicals are both products of water chemistry.

During the ring plane crossing, the radio and plasma wave science instrument on Cassini measured little puffs of plasma produced by dust impacts. While crossing the plane of Saturn's rings, the instrument detected up to 680 dust hits per second. "The particles are comparable in size to particles in cigarette smoke," said Dr. Don Gurnett of the University of Iowa, Iowa City, principal investigator for the instrument. "When we crossed the ring plane, we had roughly 100,000 total dust hits to the spacecraft in less than five minutes. We converted these into audible sounds that resemble hail hitting a tin roof."

Saturn's Moon - Titan

Titan's dense atmosphere is opaque at most wavelengths, but during a flyby, Cassini captured some surface details, including a possible crater, through wavelengths in which the atmosphere is clear. "Although the initial images appear bland and hard to interpret, we're happy to report that, with a combination of instruments, we have indeed seen Titan's surface with unprecedented clarity. We also look forward to future, much closer flybys and use of radar for much greater levels of surface detail," said Dr. Dennis Matson of NASA's Jet Propulsion Laboratory, Pasadena, CA, project scientist for the international Cassini-Huygens mission.

Titan from Cassini Cassini's visible and infrared mapping spectrometer pierced the smog that enshrouds Titan. This instrument, capable of mapping mineral and chemical features of the moon, reveals an exotic surface bearing a variety of materials in the south and a circular feature that may be a crater in the north. Near-infrared colors, some three times redder than the human eye can see, reveal the surface with unusual clarity.

"At some wavelengths, we see dark regions of relatively pure water ice and brighter regions with a much higher amount of non-ice materials, such as simple hydrocarbons. This is different from what we expected. It's preliminary, but it may change the way we interpret light and dark areas on Titan," said JPL's Dr. Kevin Baines, Cassini science-team member. "A methane cloud is visible near the south pole. It's made of unusually large particles compared to the typical haze particles surrounding the moon, suggesting a dynamically active atmosphere there."

This is the first time scientists are able to map the mineralogy of Titan. Using hundreds of wavelengths, many of which have never been used in Titan imaging before, they are creating a global map showing distributions of hydrocarbon-rich regions and areas of icy material.

Cassini's camera also sees through the haze in some wavelengths. "We're seeing a totally alien surface," said Dr. Elizabeth Turtle of the University of Arizona, Tucson. "There are linear features, circular features, curvilinear features. These suggest geologic activity on Titan, but we really don't know how to interpret them yet. We've got some exciting work cut out for us."

Since entering orbit, Cassini has also provided the first view of a vast swarm of hydrogen molecules surrounding Titan well beyond the top of Titan's atmosphere. Cassini's magnetospheric imaging instrument, the first of its kind on any interplanetary mission, provided images of the huge cloud sweeping along with Titan in orbit around Saturn. The cloud is so big that Saturn and its rings would fit within it. "The top of Titan's atmosphere is being bombarded by highly energetic particles in Saturn's radiation belts, and that is knocking away this neutral gas," explained Dr. Stamatios Krimigis of Johns Hopkins Applied Physics Laboratory, Laurel, MD, principal investigator for the magnetospheric imager. "In effect, Titan is gradually losing material from the top of its atmosphere, and that material is being dragged around Saturn."

The study of Titan, Saturn's largest moon, is one of the major goals of the Cassini-Huygens mission. Titan may preserve in deep-freeze many chemical compounds that preceded life on Earth. The July 2 flyby at a closest distance of 339,000 km (210,600 miles) provided Cassini's best look at Titan so far, but over the next four years, the orbiter will execute 45 Titan flybys as close as approximately 950 km (590 miles). This will permit high-resolution mapping of the moon's surface with an imaging radar instrument that can see through the opaque haze of Titan's upper atmosphere. In January 2005, the Huygens probe that is now attached to Cassini will descend through Titan's atmosphere to the surface.

Adapted from the information on http://www.jpl.nasa.gov/news/features.cfm?feature=590, http://www.jpl.nasa.gov/news/news.cfm?release=2004-171, http://www.jpl.nasa.gov/news/news.cfm?release=2004-170, http://www.jpl.nasa.gov/news/news.cfm?release=2004-169, and http://www.jpl.nasa.gov/news/news.cfm?release=2004-168.

(Added 07/10/04) The Hubble Heritage Team has released July's image of an HII region in the Large Magellanic Cloud (LMC) known as N11B, AKA NGC 1763. 160,000 light-years from us, the region lies in the constellation Dorado; this image covers approximately 2.2 arcminutes across (105 light-years). The image is combined from data taken on May 12, 1999, for a total exposure time of 37 minutes.

This image is a composite of two filters ([O III] (503 Å) and H-α (656 Å)), and it offers a panoramic view of glowing gas, dark dust clouds, and young, hot stars. With its high resolution, the Hubble Space Telescope is able to view details of star formation in the LMC as easily as ground-based telescopes are able to observe stellar formation within our own Milky Way galaxy. This new Hubble image zooms in on N11B, which is a small subsection within an area of star formation cataloged as N11.

N11 is the second largest star-forming region in the LMC. Within the LMC, N11 is surpassed in size and activity only by the immense Tarantula Nebula (also known as 30 Doradus.)

The image illustrates a perfect case of sequential star formation in a nearby galaxy where new star birth is being triggered by previous-generation massive stars. A collection of blue- and white-colored stars near the left of the image are among the most massive stars known anywhere in the universe. The region around the cluster of hot stars in the image is relatively clear of gas because the stellar winds and radiation from the stars have pushed the gas away. When this gas collides with and compresses surrounding dense clouds, the clouds can collapse under their own gravity and start to form new stars.

The cluster of new stars in N11B may have been formed this way, as it is located on the rim of the large, central interstellar bubble of the N11 complex. The stars in N11B are now beginning to clear away their natal cloud, and they are carving new bubbles in turn. Yet another new generation of stars is now being born in N11B, inside the dark dust clouds in the center and right-hand side of the image. This chain of consecutive star birth episodes has been seen in more distant galaxies, but it is shown very clearly in this new Hubble image.

Farther to the right of the image, along the top edge, are several smaller dark clouds of interstellar dust with odd and intriguing shapes. They are seen silhouetted against the glowing interstellar gas. Several of these dark clouds are bright-rimmed because they are illuminated and are being evaporated by radiation from neighboring hot stars.

Adapted from the information on http://heritage.stsci.edu/2004/22/.

(Added 06/30/04) Sitting within our galaxy, it is impossible for us to get a picture of what our galaxy looks like - to determine how it would appear to an outside observer. NASA's Spitzer Space Telescope, an orbiting infrared facility that began operations last year, has imaged a spiral galaxy NGC 7331, a galaxy that astronomers believe looks almost exactly as ours would appear to an outsider.

"Being inside our galaxy makes it difficult to see what's going on in the center," explained Dr. J. D. Smith, a member of the team that observed NGC 7331, and an astronomer at the University of Arizona, Tucson. "By looking at a very similar galaxy, we gain a bird's eye-view of what the entire Milky Way might look like." Such an outside perspective will teach astronomers how our own galaxy, as well as others like it, might have formed and evolved.

The latest observations are the first in a large-scale effort to observe 75 nearby galaxies with Spitzer's highly sensitive infrared eyes. Called Spitzer Infrared Nearby Galaxies Survey, the program will combine Spitzer data with that from other ground- and space-based telescopes operating at wavelengths ranging from ultraviolet to radio to create a comprehensive map of the selected galaxies.

The program's first target, NGC 7331, was chosen in part for its striking similarities to the Milky Way. While these so-called twin galaxies do not share the same parents, they have many features in common, including number of stars, mass, spiral arm pattern and star-formation rate of a few stars per year. Whether the Milky Way has an inner star-forming ring like that of NGC 7331 is not known. NGC 7331 is located about 50 million light-years away in the constellation Pegasus.

The new Spitzer image demonstrates the power of the telescope's infrared eyes to dissect galaxies into their various parts. Taken by the telescope's infrared array camera, the false-colored picture readily distinguishes NGC 7331's arms (brownish red), central bulge (blue) and star-forming ring (yellow). The composition of materials making up these regions was also revealed by the Spitzer observations: The central bulge consists primarily of older stars; the ring possesses a large amount of gas and dusty organic molecules called polycyclic aromatic hydrocarbons, which typically glow when illuminated by newborn stars; and the arms contain these same dust grains to a lesser degree. Polycyclic aromatic hydrocarbons are also found on Earth, on burnt toast and in car exhaust among other places. Data from Spitzer's infrared spectrograph instrument were also used to show that the center of NGC 7331 harbors either an unusually high concentration of massive stars, or a moderately active black hole about the same size as the one lurking at the core of our galaxy.

These findings will appear in two papers in the September issue of a special supplement to the Astrophysical Journal. Dr. Michael W. Regan of the Space Telescope Institute, Baltimore, MD, is lead author of a paper detailing observations from the infrared array camera, and Smith is lead author of a paper on the infrared spectrograph results. The Spitzer Infrared Nearby Galaxies Survey project is conducted by a team of about 25 scientists from 12 institutions, and it is led by principal investigator Dr. Robert C. Kennicutt of the University of Arizona, Tucson.

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-165.

(Added 06/27/04) Spirit, in its study of the rocks around the feet of Columbia Hills, has found hematite in the rock dubbed "Pot of Gold." Hematite was identified from orbit and it was NASA's key reason for choosing Opportunity's landing site on the other Side of Mars. Meanwhile, Opportunity continued its descent into Endurance Crater, and it has found unexpected similarities between lower layers of rock it is examining for the first time and an overlying layer at Eagle Crater - the crater in which it landed - where the rover had discovered evidence that water once soaked the area.

Mars Exploration Rover (MER) Spirit - Nuggets in the Pot of Gold - Hematite "It's gratifying how well these machines keep performing, considering they've now nearly doubled their original three-month missions on Mars," remarked Chris Voorhees, rover mechanical systems engineer at NASA's Jet Propulsion Laboratory, Pasadena, CA. By the end of next week, Spirit will have worked on Mars for half a year. It has driven more than three times the design requirement of 1 km (0.6 mile). The only symptom of wear or aging on either rover so far is increased friction in one wheel on Spirit. The rover team at JPL is beginning to consider good sites for the solar-powered robots to spend the period of martian winter when reduced daily sunshine cuts power supply to a minimum. In the nearer term, though, team members are eager to follow through on the new scientific findings.

Spirit's hematite finding is in a rock dubbed "Pot of Gold," a rock about the size of a softball. "This rock has a shape as if somebody took a potato and stuck toothpicks in it, then put jelly beans on the ends of the toothpicks," explained Dr. Steve Squyres of Cornell University, Ithaca, NY, principal investigator for the rovers' science instruments. "How it got this crazy shape is anyone's guess. I haven't even heard a good theory yet."

Dr. Doug Ming, a rover science-team member from NASA's Johnson Space Center, Houston, said, "There's apparently some type of weathering, a removal of material, but we're still trying to determine whether it's by chemical or mechanical processes." Further study of Pot of Gold could also help scientists assess what the hematite in it tells about past environmental conditions. "Hematite can form in a few different ways. Most of them require water, but it can also result from a dry, thermal oxidation process," Ming said. "It was hematite identified from orbit that made Meridiani Planum a compelling place to send Opportunity. There, we've learned that the hematite is indeed part of a water story. At Gusev we're just at the starting stage."

After examining Pot of Gold with the microscopic imager and two spectrometers on Spirit's arm, the rover backed away from the rock to re-approach at a better angle for using its rock abrasion tool to expose the rock's interior. In the rough and slippery terrain, that maneuver took several days. The other nearby rocks may also be inspected before Spirit resumes longer drives exploring the Columbia Hills area. Also, engineers are planning an attempt to redistribute lubricant in Spirit's balky right front wheel before the rover leaves its current vicinity.

Mars Exploration Rover (MER) Opportunity - Layers of Rock in Endurance Crater Team members presented both rovers' status at a press conference at JPL on June 25. Opportunity has driven far enough into the stadium-sized Endurance Crater to put it within arm's reach of three layers of rock beneath a sulfate-rich layer. That area is similar to what Opportunity first examined in the shallower "Eagle Crater," where it landed in January. "We're trying to systematically characterize the stratigraphy of the crater as we drive down, analyzing each unit chemically and mineralogically with all the instruments available," explained Nicholas Tosca, a science-team affiliate from the State University of New York, Stony Brook. The first two newly accessed layers resemble the upper layer in having sulfate salts and spherical concretions; both are signs of formation of the rocks under wet conditions.

Squyres remarked, "I had thought we might see just basalt below the top salty layer, but instead it's salty as far as we've been able to see so far. Every time we see more sulfates as we work down this stack, it adds to the amount of water that was necessary to make this happen."

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-161.

(Added 06/27/04) 170 hours of observations of the galactic center with NASA's Chandra X-ray Observatory have revealed a diffuse glow of 10 million °C gas that astronomers cannot explain. The discovery came as a result from a team of astronomers that studied a region about 100 light-years across and removed contributions from 2,357 point-like x-ray sources (neutron stars, black holes, white dwarfs, foreground stars, and background galaxies). What remained was an irregular, diffuse glow of the gas cloud, embedded in a glow of higher-energy x-rays from 100 million °C gas.

"The best explanation for the Chandra data is that the high-energy X-rays come from an extremely hot gas cloud," says Muno, lead author on a paper describing the results to appear in the September 20, 2004 issue of The Astrophysical Journal. "This would mean that there is a significant shortcoming in our understanding of heat sources in the center of our Galaxy."

The combined gravity from the known objects in the center of the Milky Way is not strong enough to prevent the escape of the 100 million degree gas from the region. The escape time would be only 10,000 years - a small fraction of the 10-billion-year age of the galaxy. This implies that the gas would have to be continually regenerated and heated.

The gas could be replenished by winds from massive stars, but the source of the heating remains a puzzle. The high-energy diffuse x-rays from the center of the galaxy appear to be the brightest part of a ridge of X-ray emission observed by Chandra and previous X-ray observatories to extend for several thousand light-years along the disk of the galaxy. The extent of this hot ridge implies that it is probably not being heated by the supermassive black hole at the center of the Milky Way.

Scientists have speculated that magnetic turbulence produced by supernova shock waves can heat the gas to 100 million degrees. Alternatively, high-energy protons and electrons produced by supernova shock waves could be the heat source. However, both these possibilities have problems. The spectrum is not consistent with heating by high-energy particles, the observed magnetic field in the galactic center does not have the proper structure, and the rate of supernova explosions does not appear to be frequent enough to provide the necessary heating.

The team also considered whether the high-energy x-rays only appear to be diffuse, and are in fact due to the combined glow of an as yet undetected population of point-like sources, like the lights of a city seen at a great distance. The difficulty with this explanation is that 200,000 sources would be required in the observed region. Although the total number of stars in this region is about 30 million, the number of stars of the type expected to produce x-rays at the required power and energy is estimated to be only 20,000. Further, such a large unresolved population of sources would produce a much smoother x-ray glow than is observed.

"There is no known class of objects that could account for such a large number of high-energy X-ray sources at the Galactic center," said Fred Baganoff of the Massachusetts Institute of Technology (MIT) in Cambridge, a coauthor of the study.

Adapted from the information on http://chandra.harvard.edu/press/04_releases/press_062104.html.

(Added 06/20/04) Four years after an international team of scientists began, they have now, for the first time, measured the mass of and ultra-cool star and its brown dwarf companion. The two form a binary system with an orbital period of about 10 years.

Even though astronomers have found several hundred very low-mass stars and brown dwarfs, the fundamental properties of these extreme objects, such as masses and surface temperatures, are still not well known. Within the cosmic zoo, these ultra-cool stars represent a class of "intermediate" objects between giant planets - like Jupiter - and "normal" stars less massive than our sun, and to understand them well is crucial to the field of stellar astrophysics.

The problem with these ultra-cool stars is that - contrary to normal stars that burn hydrogen in their central core - no unique relation exists between the luminosity of the star and its mass. Indeed, luminosities and surface temperatures of ultra-cool dwarf stars depend both on their age and their mass. An older, somewhat more massive ultra-cool dwarf can thus have exactly the same temperature as a younger, less massive one. It is a basic goal of modern astrophysics to obtain independently the masses of an ultra-cool dwarf star. This is in principle possible by studying such objects that are members in a binary system.

This is precisely what an international team of astronomers has now done in a four-year long study of a binary stellar system with an ultra-cool dwarf star, using a plethora of top telescopic facilities, including the European Southern Observatory's Very Large Telescope, Keck I, and Gemini North in Hawaii, and also the Hubble Space Telescope. This system - with the telephone number name of 2MASSW J0746425+2000321 - is located at a distance of 40 light-years from Earth.

The astronomers used high-angular-resolution imaging to see both stars in the binary system and to measure their motion over a four-year period. However, this is more easily said than done, as the separation on the sky between the two stars is quite small: between 0.13 and 0.22 arcsec. This separation is so small that it is normally not possible to differentiate the two stars due to the blurring effect of atmospheric turbulence (the "seeing"). It is therefore necessary to use the technique of adaptive optics. This is based on the measurement of the image quality in real-time and sending corresponding corrective signals up to 100 times every second to a small deformable mirror, located in front of the detector. As the mirror continuously modifies its shape, the disturbing effect of the turbulence is neutralized. Applied at the VLT, this technique has resulted in images which are at least ten times sharper than the seeing and which therefore show many more details in the observed objects.

During their four-year long study, seven different relative positions of the two components of the binary system were measured and Hervé Bouy and his co-workers were able to determine with good precision the stellar orbits. They find that the two stars revolve around each other once every 10 years and that their physical separation is only 2.5 times the distance of the Earth to the Sun. Using Kepler's laws, it is then straightforward to derive the total mass of the system. The obtained value is less than 15% of the mass of the sun.

The astronomers then used the photometric data of each star obtained in several wavebands, as well as spectra obtained with the Hubble Space Telescope to study the two objects in more detail. Using the latest stellar models of the group of the Ecole Normale Supérieure de Lyon, they found that both stars have roughly the same surface temperature, around 1800 K - about 3 times cooler than our sun.

Using theoretical models, the team also found that the two stars are rather young - their age is between 0.5-1.0 billion years. The more massive of the two has a mass between 7.5 and 9.5% the mass of the sun, while its companion has a mass between 5 and 7% of the solar mass. Objects weighing less than about 7% of our sun have been called "Brown Dwarfs", "Failed Stars" or "Super Planets". Indeed, since they have no sustained energy generation by thermal nuclear reactions in their interior, many of their properties are more similar to those of giant gas planets in our own solar system such as Jupiter, than to stars like the Sun.

Therefore, the system 2MASSW J0746425+2000321 is comprised of a brown dwarf orbiting a slightly more massive ultra-cool dwarf star. It is a true "Rosetta stone" in the new field of low-mass stellar astrophysics, and further studies will surely provide more valuable information about these objects in the transitional zone between stars and planets.

Adapted from the information on http://www.eso.org/outreach/press-rel/pr-2004/pr-16-04.html.

(Added 06/20/04) Findings from a historic encounter between NASA's Stardust spacecraft and a comet have revealed a much stranger world than previously believed. The comet's rigid surface, dotted with towering pinnacles, plunging craters, steep cliffs, and dozens of jets spewing violently, has surprised scientists.

"We thought Comet Wild 2 would be like a dirty, black, fluffy snowball," explained Stardust Principal Investigator Dr. Donald Brownlee of the University of Washington, Seattle. "Instead, it was mind-boggling to see the diverse landscape in the first pictures from Stardust, including spires, pits and craters, which must be supported by a cohesive surface."

Stardust gathered the images on January 2, 2004, when it flew 236 km (about 147 miles) from Wild 2. The flyby yielded the most detailed, high-resolution comet images ever.

"We know Wild 2 has features sculpted by many processes. It may turn out to be typical of other comets, but it is unlike any other type of solar system body," Brownlee said. He is lead author of one of four Stardust papers appearing in the Friday, June 18, issue of Science. "We're fortunate that nature gave us such a rich object to study.”

Stardust images show pinnacles 100 m tall (328 ft), and craters more than 150 m deep (492 ft). Some craters have a round central pit surrounded by ragged, ejected material, while others have a flat floor and straight sides. The diameter of one large crater, called Left Foot, is 20% of the surface of the comet. Left Foot is 1 km (0.6 miles) across, while the entire comet is only 5 km (3.1 miles) across.

"Another big surprise was the abundance and behavior of jets of particles shooting up from the comet's surface. We expected a couple of jets, but saw more than two dozen in the brief flyby," said Dr. Benton Clark, chief scientist of space exploration systems, Lockheed Martin Space Systems, Denver. The team predicted the jets would shoot up for a short distance, and then be dispersed into a halo around Wild 2. Instead, some super-speedy jets remained intact, like blasts of water from a powerful garden hose. This phenomenon created quite a wild ride for Stardust during the encounter.

"Stardust was absolutely pummeled. It flew through three huge jets that bombarded the spacecraft with about a million particles per second," said Thomas Duxbury, Stardust project manager at NASA's Jet Propulsion Laboratory, Pasadena, CA. Twelve particles, some larger than a bullet, penetrated the top layer of the spacecraft's protective shield. The violent jets may form when the sun shines on icy areas near or just below the comet's surface. The solid ice becomes a gas without going through a liquid phase. Escaping into the vacuum of space, the jets blast out at hundreds of kilometers per hour.

The Stardust team theorizes sublimation and object hits may have created the comet's distinct features. Some features may have formed billions of years ago, when life began on Earth, Brownlee suggested. Particles collected by Stardust during the Wild 2 encounter may help unscramble the secrets of how the solar system formed.

Stardust was launched in 1999. It is zooming back to Earth with thousands of captured particles tucked inside a capsule. The capsule will make a soft landing in the Utah desert in January 2006. The samples will be analyzed at the planetary material curatorial facility at NASA's Johnson Space Center, Houston, TX. Comets have been objects of fascination through the ages. Many scientists believe they delivered carbon and water, life's building blocks, to Earth. Yet their destructive potential is illustrated by the widely held theory that a comet or asteroid wiped out the dinosaurs.

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-154.

(Added 06/20/04) Cassini, en route to Saturn since 1996, flew by one of Saturn's outermost moons, Phoebe, with the closest approach occurring on June 11, 2004 at approximately 1:56 P.M. PDT, just 19 days before Saturn arrival. On arrival date, June 30, Cassini will become the first spacecraft to orbit Saturn. Once in orbit it will conduct an extensive, four-year tour of the Saturn system, including its majestic rings and many known moons.

Saturn's Moon Phoebe as Seen by Cassini "The last time we had observations of Phoebe was by Voyager in 1981," said Dr. Torrence Johnson, former Voyager imaging team member, Galileo project scientist and current Cassini imaging team member. "This time around, the pictures of the mysterious moon will be about 1,000 times better, as Cassini will be closer." Voyager 2 captured images of Phoebe from about 2.2 million km (about 1.4 million miles) away. Cassini obtained images from a mere 2,000 km (about 1,240 miles) above the moon's surface.

Discovered in 1898 by American astronomer William Henry Pickering, Phoebe is of great interest to scientists. "With the instruments Cassini carries, we might learn more about Phoebe's internal structure and composition. What we have are many unanswered questions: Did it ever melt? Does it have evidence of past interior melting? Was it ever an icy body? Why is Phoebe in such an odd orbit?" asked Dr. Dennis Matson, project scientist for the Cassini-Huygens mission at JPL.

Phoebe has a diameter of 220 km (about 136.7 miles), which is equal to about 1/15 the diameter of Earth's moon. Phoebe rotates on its axis every nine hours and 16 minutes, and it completes a full orbit around Saturn in about 18 months. Its elliptical orbit is inclined approximately 30 degrees to Saturn's equator. Phoebe's retrograde orbit means that it goes around Saturn in the opposite direction of the larger interior Saturnian moons. Previous ground-based observations have shown water ice present on its surface.

Phoebe is also unusual in that it is very dark. It reflects only 6% of the sunlight it receives. Phoebe's darkness and retrograde orbit suggest that it is most likely a captured object. A captured object is a celestial body that is caught by the gravitational pull of a much bigger body, generally a planet. Some scientists believe Phoebe might even be an object from the outer solar system, similar to the objects found in the Kuiper Belt. The Kuiper Belt is a collection of small icy bodies beyond Pluto that were never drawn together by gravity to form a planet.

"The dark and odd-shaped Phoebe may be a piece of the building blocks from which some of the planets formed," said Dr. Bonnie Buratti, scientist on the Cassini-Huygens mission at JPL. "It might hold clues about the early formation of our solar system."

The first images from the Cassini flyby of Phoebe reveal it to be a scarred, cratered outpost with a very old surface and a mysterious past, and a great deal of variation in surface brightness across its surface. "What spectacular images," said Dr. Carolyn Porco, Cassini Imaging Team leader at the Space Science Institute in Boulder, CO. "So sharp and clear and showing a great many geological features, large and small. It's obvious a lot of new insights into the origin of this strange body will come as a result of all this."

Dr. Gerhard Neukum, an imaging team member from Freie University in Berlin, remarked, "It is very interesting and quite clear that a lot of craters smaller than a kilometer are visible. This means, besides the big-ones, lots of projectiles smaller than 100 m (328 feet) have hit Phoebe." Whether these projectiles came from outside or within the Saturn system is debatable.

Close-Up of Phoebe as Seen from Cassini There is a suspicion that Phoebe, the largest of Saturn's outer moons, might be parent to the other, much smaller retrograde outer moons that orbit Saturn. Dr. Joseph Burns, an imaging team member and professor at Cornell University, Ithaca, NY, said, "Looking at those big 50 km (31 mile) craters, one has to wonder whether their impact ejecta might be the other tiny moons that orbit Saturn on paths much like Phoebe's."

All planned 11 instruments operated as expected and all data was acquired. Scientists plan to use the data to create global maps of the cratered moon, and to determine Phoebe’s composition, mass and density. It will take scientists several days to pour over the data to make more concrete conclusions. Cassini came within approximately 2,068 km (about 1,285 miles) of the dark moon. The spacecraft was pointing its instruments at the moon during the flyby. Several hours later it turned to point its antenna to Earth. The signal was received through the Deep Space Network antennas in Madrid, Spain and Goldstone, in California’s Mojave Desert, at 7:52 A.M. PDT on June 12. Cassini was traveling at a relative speed of 20,900 kph (13,000 mph) relative to Saturn.

Images collected during Cassini's close flyby of Saturn's moon, Phoebe, have yielded strong evidence that the tiny object may contain ice-rich material, overlain with a thin layer of darker material perhaps 300 to 500 m (980 to 1,600 ft) thick. The surface of Phoebe is also heavily potholed with large and small craters. Images reveal bright streaks in the ramparts of the largest craters, bright rays which emanate from smaller craters, and uninterrupted grooves across the face of the body.

"The imaging team is in hot debate ... on the interpretations of our findings," said Dr. Carolyn Porco. "Based on our images, some of us are leaning towards the view that has been promoted recently, that Phoebe is probably ice-rich and may be an object originating in the outer solar system, more related to comets and Kuiper Belt objects than to asteroids."

In ascertaining Phoebe's origin, imaging scientists are noting important differences between the surface of Phoebe and that of rocky asteroids which have been seen at comparable resolution. "Asteroids seen up close, like Ida, Mathilde, and Eros, and the small martian satellites do not have the bright 'speckling' associated with the small craters that are seen on Phoebe," explained Dr. Peter Thomas. The landforms observed in the highest resolution images also contain clues to the internal structure of Phoebe. Dr. Alfred McEwen, an imaging team member from the University of Arizona, Tucson, said, "Phoebe is a world of dramatic landforms, with craters everywhere, landslides, and linear structures such as grooves, ridges, and chains of pits. These are clues to the internal properties of Phoebe, which we'll be looking at very closely in order to understand Phoebe's origin and evolution."

Close-Up of Phoebe's South Pole, Seen from Cassini "I think these images are showing us an ancient remnant of the bodies that formed over four billion years ago in the outer reaches of the solar system," said Dr. Torrence Johnson. "Battered and beat-up as it is, it is still giving us clues to its origin and history."

With the Phoebe accomplished, Cassini is on course for Saturn. A trajectory correction maneuver is scheduled for June 16. Cassini will conduct a critical 96-minute burn before going into orbit around Saturn on June 30 (July 1 Universal Time). During Cassini's planned four-year tour it will conduct 76 orbits around the Saturn system and execute 52 close encounters with seven of Saturn’s 31 known moons.

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-145, http://www.jpl.nasa.gov/news/news.cfm?release=2004-147, http://www.jpl.nasa.gov/news/news.cfm?release=2004-149.

(Added 06/20/04) With over 3.4 km on its odometer, Mars Exploration Rover (MER) Spirit has finally reached Columbia Hills, as of June 10. Spirit began climbing the hills, and it right away sent back tantalizing pictures of rocks.

"Some of the rocks appear to be disintegrating. They have an odd kind of rotting appearance, with soft interiors and resistant rinds or hulls," said Dr. Larry Soderblom, a rover science-team member from the U.S. Geological Survey, Flagstaff, AZ. "The strangest things we've encountered are what we're calling hooded cobras, which are evidently the resistant remnants of some of those rocky rinds. They stand above the surface like small canopies."

Another rock, dubbed "Pot of Gold," appears to have nodules and resistant planes in a softer matrix. Scientists have chosen it as a target for Spirit to examine with the instruments on the rover's robotic arm. Afterwards, controllers plan to send Spirit to an outcrop farther uphill. "Although it's too early to even speculate as to the processes these rocks have recorded, we are tremendously excited over the new prospects," Soderblom said.

The Columbia Hills rise approximately 90 m (about 300 ft) above a plain Spirit crossed to reach them. Scientists anticipate a complex blend of rocks in the hills, perhaps holding evidence about a broader range of environmental conditions than has been seen in the volcanic rubble surfacing the plain. The entire area Spirit is exploring is within Gusev Crater. Orbital images suggest water may have once flowed into this Connecticut-sized basin.

Meanwhile, halfway around Mars, MER Opportunity entered Endurance Crater on June 8. Even with the risk that the craft might not be able to climb back out, mission scientists decided that the possible scientific gains outweigh the risks. The target for inspection is a rock outcrop in the crater that corresponds with what Opportunity studied in Eagle Crater that it landed in in January. The plan for crater travel is to keep all six wheels on rocks and not sand. Tests with mock-ups on Earth indicate that as long as the slope does not go above 25°, there is a significant safety margin.

Opportunity's first target inside the crater was a flat-lying stone about 36x15 cm (14x6 in.) dubbed "Tennessee" for its shape. Opportunity will inspect it for analysis with the spectrometers and microscopic imager on the rover's robotic arm. It is in a layer geologists believe corresponds to sulfate-rich rocks. The rocks are similar to those, in which Opportunity previously found evidence for a body of water covering the ground long ago.

"The next step will be to move farther down from this layer to our first close-up look at a different sedimentary sequence," McLennan said. "Color differences suggest at least three lower, older layers are exposed below Opportunity's location. The interpretation of those lower units is in a state of flux. At first, we thought we would encounter poorly consolidated, sandy material. But as we get closer, we're seeing more-consolidated, harder rock deeper into the crater. If we can get to the lower units, this will be the first detailed stratigraphic section ever done on another planet. We're doing exactly what a field geologist would be doing."

Spirit is showing what may be the first sign of age and wear. "The right front wheel is drawing about two to three times as much current as the other wheels, and that may be a symptom of degradation," Adler said. "There may be steps we can take to improve it. We'll be studying that possibility during the next few weeks."

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-144 and http://www.jpl.nasa.gov/news/news.cfm?release=2004-152.

(Added 06/20/04) 30 million light-years from Earth lies either the youngest black hole or the youngest neutron star known in the entire universe. The astronomers used a global combination of radio telescopes to study the stellar explosion, and their discovery marks the first time that a black hole or neutron star has been found associated with a supernova that has been seen to explode since the invention of the telescope nearly 400 years ago.

The team studied a supernova called SN 1986J in a galaxy called NGC 891. The supernova was discovered in 1986, but the astronomers believe the explosion actually happened 3 years earlier. They used the National Science Foundation's Very Long Baseline Array (VLBA), Robert C. Byrd Green Bank Telescope (GBT), and Very Large Array (VLA), along with radio telescopes from the European VLBI Network. They made images that showed fine details of how the explosion evolves over time.

"SN 1986J has shown a brightly-emitting object at its center that only became visible recently. This is the first time such a thing has been seen in any supernova," said Michael Bietenholz, of York University in Toronto, Ontario. Bietenholz worked with Norbert Bartel, also of York University, and Michael Rupen of the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico, on the project. "A supernova is likely the most energetic single event in the universe after the Big Bang. It is just fascinating to see how the smoke from the explosion is blown away and how now after all these years the fiery center is unveiled. It is a textbook story, now witnessed for the first time," Bartel said.

Analysis of the bright central object shows that its characteristics are different from the outer shell of explosion debris in the supernova. "We can't yet tell if this bright object at the center is caused by material being sucked into a black hole or if it results from the action of a young pulsar, or neutron star," said Rupen. "It's very exciting because it's either the youngest black hole or the youngest neutron star anybody has ever seen." The youngest pulsar found to date is 822 years old.

"We'll be watching it over the coming years. First, we hope to find out whether it's a black hole or a neutron star. Next, whichever it is, it's going to give us a whole new view of how these things start and develop over time," Rupen said. For example, Rupen explained, if the object is a young pulsar, learning the rate at which it is spinning and the strength of its magnetic field would be extremely important for understanding the physics of pulsars.

Adapted from the information on http://www.nrao.edu/pr/2004/sn1986j/, and the research appeared in the June 10 issue of Science Express.

(Added 06/03/04) The Hubble Heritage Team has released June's image of the emission nebula and HII region known as M20, NGC 6514, and more commonly as the Trifid Nebula. 9,000 light-years from us, M20 lies in the constellation Sagittarius; this image covers approximately 3.9 arcminutes across (10.2 light-years). The image is combined from data taken on June 3, July 5, and August 1, 2001, and June 18 & 22, 2002, for a total exposure time of 1.7 hours.

This image is a composite of three filters ([O III] (503 Å), H-α (656 Å), and [S II] (673 Å)), and it offers a close-up view of the nebula's center, a well-known region of star formation in our galaxy. It is called the Trifid because the nebula is overlain by three bands of obscuring interstellar dust, giving it a trisected appearance as seen in small telescopes. This image is centered near the intersection of the dust bands, where a group of recently formed, massive, bright stars is easily visible.

These stars, which are classified as belonging to the hottest and bluest types of stars called "O," are releasing a torrent of ultraviolet radiation that dramatically affects the structure and evolution of the surrounding nebula. Many astronomers who study nebulae like the Trifid are focusing their research on the ways that waves of star formation move through such regions.

The group of bright stars at the center in this image illuminates a dense pillar of gas and dust, seen to the right of the center, producing a bright rim on the side that faces the stars. At the upper left tip of this pillar, there is a complex filamentary structure that is bluish in color - this color is from glowing oxygen gas that is evaporating into space. Star formation is no longer occurring in the immediate vicinity of the group of bright stars because their intense radiation has blown away the gas and dust from which the stars are made.

Adapted from the information on http://heritage.stsci.edu/2004/17/.

(Added 06/02/04) Nebulae are clouds of dust and gas that have no intrinsic optical light of their own. We see them illuminated by other objects, usually stars. However, today at the meeting of the American Astronomical Society in Denver CO, Smithsonian astrophysicist Philip Kaaret (Harvard-Smithsonian Center for Astrophysics) announced that one nebula is illuminated by x-rays from a black hole. Moreover, the brightness of the nebula suggests that the x-ray source may be an intermediate-mass black hole many times larger than most stellar black holes.

This surprising find offers only the second known example of a black hole-illuminated nebula, with the LMC X-1 in the Large Magellanic Cloud being the first; this is the first example of a nebula powered by an intermediate-mass black hole. "Astronomers always get excited about new things, and this nebula is certainly something new. Finding it is like getting a royal flush the first time you play poker - it's that rare," said Kaaret.

Initially discovered by Manfred Pakull and Laurent Mirioni (University of Strasbourg), the nebula is located 10 million light-years away in the dwarf irregular galaxy Holmberg II. Two years ago, Pakull and Mirioni noted that it seemed to be associated with an ultraluminous x-ray source. By combining observations from NASA's Hubble Space Telescope and Chandra X-ray Observatory with those from ESA's XMM-Newton spacecraft, Kaaret and his colleagues - Martin Ward (University of Leicester) and Andreas Zezas (CfA) - pinpointed the x-ray source at the center of the nebula. Moreover, the mystery source is pouring out x-rays at a tremendous rate, shining one million times brighter in x-rays than the sun shines at all wavelengths of light combined.

The observations indicate that those x-rays are generated by a black hole accreting matter from a young, massive companion star at a rate of about one Earth mass every four years. That modest accretion rate is sufficient to ionize and light up a huge 100-light-year-wide swath of the surrounding nebula.

The x-ray emissions provide an important clue to the nature of the black hole. Some astronomers have suggested that x-rays from the source in Holmberg II and similar bright sources are beamed in the Earth's direction like a searchlight. Such beaming would make the x-ray source appear brighter than it really is, thereby making the black hole appear more massive than it really is. Kaaret's data contradict that view, showing instead that the black hole in Holmberg II sends out x-rays evenly in all directions. Therefore, its brightness suggests that it must be more massive than any stellar black hole in our own Galaxy, weighing in at more than 25 times the mass of the sun and likely more than 40 solar masses. That would rank it as an "intermediate-mass" black hole.

"It's not easy to explain how intermediate-mass black holes form. Since we only have a few examples to study, every new find is important," said Kaaret.

Adapted from the information on http://cfa-www.harvard.edu/press/pr0422.html, and the research will appear in an upcoming issue of the Monthly Notices of the Royal Astronomical Society.

(Added 06/02/04) Gamma-ray bursts (GRBs), are believed to represent some of the most energetic explosions in the universe, originating outside of our galaxy yet, for a brief period, becoming the largest gamma-ray source other than the sun in the sky. Astronomers using NASA's Chandra X-ray Observatory and infrared observations with the Palomar 200-inch telescope have uncovered evidence that a GRB occurred within our own galaxy a few thousand years ago.

The supernova remnant is known as W49B, and it may also be the first remnant of a GRB discovered in the Milky Way. W49B is barrel-shaped, and it is located about 35,000 light-years from Earth. The new data show bright rings in the infrared, like hoops about a barrel, and they show intense x-rays from iron and nickel along the axis of the barrel.

"These results provide intriguing evidence that an extremely massive star exploded in two powerful, oppositely directed jets that were rich in iron," said Jonathan Keohane of NASA's Jet Propulsion Laboratory at a press conference at the American Astronomical Society meeting in Denver, CO. "This makes W49B a prime candidate for being the remnant of a gamma ray burst involving a black hole collapsar."

"The nearest known gamma-ray burst to Earth is several million light-years away - most are billions of light-years distant - so the detection of the remnant of one in our galaxy would be a major breakthrough," said William Reach, one of Keohane's collaborators from the California Institute of Technology.

The collapsar theory holds that GRBs are produced when a massive star runs out of fuel and the star's core collapses to form a black hole surrounded by a disk of extremely hot, rapidly rotating, magnetized gas. Most of the gas is pulled into the black hole, but some is shot away in oppositely directed jets of gas traveling at nearly the speed of light. An observer aligned with one of the jets would see a GRB - a blinding flash in which the concentrated power equals that of 10 quadrillion times the sun for a minute or so. If an observer is perpendicular to the jets, the view is not as exciting, but it is still a supernova explosion.

For W49B, the jet is tilted out of the plane of the sky by about 20°; four rings, about 25 light-years in diameter, can be identified in the infrared image. The rings are from warm gas, and they were presumably created when the gas was flung out by the rapid rotation of the massive star a few hundred thousand years before the star exploded. The rings were pushed outward by an intense solar wind from the star a few thousand years before the final explosion.

The evidence for this to be a GRB remnant lie in the spectral data from Chandra: Jets of multimillion °C gas extend along the axis of the barrel and are rich in iron and nickel ions, consistent with their being ejected from the center of the star. This distinguishes W49B from a conventional Type II supernova in which most of the Fe and Ni goes into making the neutron star, and the outer part of the star is what is flung out. In the collapsar model, the Fe and Ni from the center is ejected along the jet.

At the barrel ends, the x-ray emission flares out to make a "cap." The x-ray cap is surrounded by a flattened cloud of hydrogen molecules detected in the infrared. These features indicate that the shock wave produced by the explosion has encountered a large, dense cloud of gas and dust.

The scenario that emerges from these observations is one in which a massive star formed from a dense cloud of dust, shone brightly for a few million years while spinning off rings of gas and pushing them away, forming a nearly empty cavity around the star. The star then underwent a collapsar-type supernova explosion that resulted in a gamma-ray burst.

The observations of W49B may help to resolve a problem that has bedeviled the collapsar model for gamma-ray bursts. On the one hand, the model is based on the collapse of a massive star, which is normally formed from a dense cloud. On the other hand, observations of the afterglow of many gamma-ray bursts indicate that the explosion occurred in a low-density gas. Based on the W49B data, the resolution proposed by Keohane and colleagues is that the star had carved out an extensive low-density cavity in which the explosion subsequently occurred. "This star appears to have exploded inside a bubble it had created," said Keohane. "In a sense, it dug its own grave."

Adapted from the information on http://chandra.harvard.edu/press/04_releases/press_060204.html.

(Added 06/01/04) The Pinwheel Galaxy, more officially named M33, is one of the nearest large galaxies to our own. When scientists study the Pinwheel, they can find clues to how galaxies like ours are born, live, and die. At today's meeting of the American Astronomical Society in Denver, CO, astronomers from the University of Minnesota, the Harvard-Smithsonian Center for Astrophysics (CfA), and the University of Arizona unveiled new infrared images of M33 taken by NASA's Spitzer Space Telescope. The photos reveal features of the galaxy never before visible.

M33 - Pinwheel Galaxy - taken by Spitzer Space Telescope (SST) About 50,000 light-years across, the spiral galaxy M33 is about half the diameter of the Milky Way. It lies 3 million light-years from the Milky Way, which places it among the Local Group of galaxies. Its nearness and viewing angle give astronomers an excellent opportunity to study M33's physical and chemical processes.

"With the Andromeda Galaxy, it's one of the two nearest large spiral galaxies comparable to the Milky Way. Since it's so close, we can get a nice panoramic view. It's a great object for detailed study," correlated Smithsonian astronomer Steven Willner (CfA).

"M33 is a gigantic laboratory where you can watch dust being created in novae and supernovae, being distributed in the winds of giant stars, and being reborn in new stars," added University of Minnesota researcher and lead author Elisha Polomski. By studying M33, "you can see the Universe in a nutshell."

Because it operates at infrared wavelengths, the Spitzer Space Telescope detects details hidden to the human eye and to telescopes that operate in visible light. Spitzer collects light at wavelengths measured in microns (µm) - millionths of a meter. The new pictures were taken in light at wavelengths ranging from 3.5 to 24 µm.

"At 3.5 µm, we see stars," explained University of Minnesota astronomy professor Robert Gehrz, a member of the M33 observation team. "At 8 µm, we see warm dust that's about 130 °F. At 24 µm, we're picking up cool dust that's between -100 and -190 °F." Spitzer's cameras also operate at 70 and 160 µm.

Observations of M33's cool components are expected to reveal much about the "metabolism" of galaxies. A galaxy is akin to a living body, in which food substances are broken down to build the body, and the waste and decomposition products of a body are recycled to feed new life. For example, the iron in Earth's core was forged in the bellies of large, luminous stars, and the heavier elements - all the way to uranium, the heaviest naturally occurring element - were created in supernova explosions. The deaths of those stars sprayed interstellar space with dust and gas, some of which clumped together in a disk that coalesced to form the sun and its planets.

The Spitzer team will examine the Pinwheel Galaxy in detail for the next two and a half years, studying the processes that circulate energy and chemical elements through the galaxy to build up, destroy, and recycle the building blocks of stars and planets. The researchers expect to identify new star-forming regions, red giant stars, novae and supernovae, thereby mapping out the evolutionary process of stars in M33 and comparing it to the process in our own Galaxy.

Adapted from the information on http://cfa-www.harvard.edu/press/pr0421.html.

(Added 06/01/04) The Pleiades, an open star cluster, has had a controversy surrounding its distance for the past seven years - ever since the European Hipparcos satellite measured a distance to it 10% shorter than the previously accepted distance. In January of this year, a team of astronomers measured the distance to a star in the cluster, agreeing with the larger distance.

Now, NASA's Hubble Space Telescope has weighed in on the controversy. Measurements made by Hubble's Fine Guidance Sensors show that the distance is about 440 light-years from Earth, essentially the same as past distance estimates, including those released in January, and differing from Hipparcos by more than 40 light-years. The Hubble results were presented today at the American Astronomical Society meeting in Denver, CO.

The image at the right shows the various fields that Hubble examined, superimposed upon a larger image from the Digitized Sky Survey.

The discrepancy in the distance to the Pleiades is more than an arcane argument over details. Astronomers have only one direct means for gauging distances to stars, called the parallax method. With current telescopes, this method gives accurate results only for distances up to about 500 light-years. Distances beyond that limit must be determined by indirect methods, based on comparing the brightness of distant stars with those of nearer ones of the same type, and making the assumption that both objects have the same intrinsic, or true, brightness. Astronomers can thus build up a distance ladder, based on ever more-distant objects, ultimately leading to the use of supernovae as "standard candles" for the most distant reaches of the universe.

"Reliance on the accuracy of the measurements of nearby objects is crucial to getting the distance ladder of the universe correct," emphasized David Soderblom of the Space Telescope Science Institute in Baltimore, MD, and lead astronomer on the Hubble study. "The new Hubble result shows that the measurements made by Hipparcos contain a small, but significant, source of error that requires further exploration. New space missions are now being planned to carry out even more precise distance measurements out to greater distances."

Soderblom and his team used Hubble's Fine Guidance Sensors to measure slight changes in the apparent positions of three stars within the cluster when viewed from different sides of Earth's orbit. Due to the motion of the Earth around the sun, the position of a star in the Pleiades will appear to shift relative to stars farther away. This effect, called parallax, can be used to calculate the distance to the star with simple geometry; a similar method of triangulation is used by surveyors to measure distances on Earth. Soderblom's team took its measurements six months apart over a 2 1/2-year period.

Making these kinds of measurements of a star's movement is very difficult. The Fine Guidance Sensors are so precise that if the human eye had the same ability to measure small angles, it would be able to see a quarter 16,000 miles away. Hipparcos was the first space observatory to make precise measurements of the positions and motions of celestial objects. Before Hipparcos, astronomers determined the distances to stars like the Pleiades by measuring parallax with ground-based telescopes. Those observations were less precise because Earth's atmosphere distorts light from stars, limiting the telescopes' resolution.

Adapted from the information on http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/20/.

(Added 06/01/04) NASA's Great Observatories program involves four space-based telescopes: Compton Gamma-ray Observatory, Hubble Space Telescope, Chandra X-ray Observatory, and Spitzer Space Telescope. All four were designed to explore the universe in different wavelengths to reveal different information. One of the legacy projects for Spitzer, the newest and last of the Great Observatories, is the Great Observatories Origins Deep Survey (GOODS) - to use the telescopes to peer into the same regions of the sky.

Today at the American Astronomical Society's meeting in Denver, CO, the deepest Spitzer images were displayed, and they contain many distant objects, including supermassive black holes, that are nearly invisible at other wavelengths, underscoring the significance of using the four telescopes in tandem. Seven of the objects detected by Spitzer may be part of the long-sought population of "missing" supermassive black holes that powered the bright cores of the earliest active galaxies. The discovery completes a full accounting of all the x-ray sources seen in one of the deepest surveys of the universe ever taken.

Dr. Mark Dickinson, of the National Optical Astronomy Observatory, Tucson, AZ, principal investigator for the new observations, said "with these ultra-deep Spitzer images, we are easily seeing objects throughout time and space, where the most distant known galaxies lie. Moreover, we see some objects that are completely invisible, but whose existence was hinted at by previous observations from the Chandra and Hubble Observatories."

This particular detective story required the combined power of NASA's three Great Observatories - the Hubble Space Telescope, Chandra X-ray Observatory and Spitzer Space Telescope. All three telescopes looked as far as 13 billion light-years away, toward a small patch of the southern sky containing more than 10,000 galaxies. Chandra images detected more than 200 x-ray sources believed to be supermassive black holes in the centers of young galaxies (extremely hot interstellar gases falling into the black holes produce the x-rays).

Hubble's Advanced Camera for Surveys revealed optical galaxies around almost all the x-ray black holes. However, seven mysterious x-ray sources remained for which there was no optical galaxy. Dr. Anton Koekemoer of the Space Telescope Science Institute, Baltimore, MD, discovered these sources and has three intriguing possibilities for their origin: "The galaxies around these black holes may be completely hidden by thick clouds of dust absorbing all their light, or may contain very old, red stars. Or some could be the most distant black holes ever observed -- perhaps as far as 13 billion light-years." If so, all their optical light would be shifted to very long infrared wavelengths by expansion of the universe.

Scientists eagerly awaited the Spitzer images to solve this puzzle. Because Spitzer observes at infrared wavelengths up to 100 times longer than those probed by Hubble, Spitzer might have been able to see the otherwise invisible objects. Indeed, the very first Spitzer images of these objects, obtained earlier this year, immediately revealed the telltale infrared glow from the host galaxies around all the missing x-ray black holes. Three of Koekemoer's galaxies are extremely "red," or bright, in infrared. The Spitzer data, together with new images at shorter infrared wavelengths from the Very Large Telescope at the European Southern Observatory, indicate that the galaxies around these black holes could be heavily obscured by dust, and perhaps more distant than other known dust-obscured galaxies.

Some of the other objects, however, have quite different colors, and are even more intriguing. "Their colors may be consistent with objects more distant than any now known," said Dickinson, who cautioned that additional Spitzer observations later this year will help confirm what kind of objects these might be.

In another study using the same Spitzer data, Dr. Haojing Yan of the California Institute of Technology, Pasadena, CA, studied 17 unusual galaxies near the Hubble Ultra Deep Field. This small patch of sky within the GOODS area was recently the target for the deepest optical images ever taken with Hubble's Advanced Camera. The Deep Field optical images, released in March 2004, reach more than five times fainter than the GOODS Hubble data. But even with that phenomenal sensitivity, two of the 17 Spitzer-selected objects remain completely invisible in optical light, while the others are only faintly detected. Yan finds that these galaxies get steadily brighter at longer wavelengths, and seem to be more distant cousins of the so-called "Extremely Red Objects," known from previous deep surveys. Most are distant galaxies that are red because they are either old or dusty. These new Spitzer-identified objects, however, appear to lie farther away in a time when the universe was only two billion years old.

"These objects could be the remnants of the first stars -- the very first galaxies formed in the earliest stages of the universe," explained Yan. Most galaxies that we see today formed their stars gradually over a long period of time. But these 17 objects seem to be "old before their time," perhaps almost as old as the universe itself at that early epoch. "If we indeed are seeing the direct, 'pure' descendants of the first stars, this would make a thrilling story," says Yan. Further Spitzer observations at longer wavelengths, planned for later this year, should help decide whether these objects are red because they are old, or because they are young and actively forming stars enveloped in dust.

Using Hubble and Chandra data, Dr. Meg Urry, a GOODS astronomer at Yale University, New Haven, CN, and her team suggest that most accreting black holes are hidden at visible wavelengths, even in the early universe. Few such hidden black holes had previously been found at such large distances, despite theoretical arguments for their existence. They were missed because their visible radiation is so dim they look like faint, ordinary galaxies. "With the new Spitzer data these very luminous, distant objects are easily visible," said Urry. "The great sensitivity of the new Spitzer infrared cameras, combined with the superb spatial resolution of Chandra, means that finding all of the black holes that are powered by infalling gas is now possible."

Urry's team is using data from the three space observatories to take a census of the supermassive black holes that formed two to five billion years after the big bang. Most of these active galactic nuclei are hidden by dust, which absorbs visible and some x-ray light but emits strongly at infrared wavelengths. "The Spitzer GOODS observations verify that large numbers - perhaps three-quarters - of the obscured active galactic nuclei were indeed present in the early universe. The longer-wavelength Spitzer data still to come will reveal even more shrouded active galactic nuclei," said Urry, "including some, missed by x-ray observations, which look like ultraluminous infrared galaxies."

Adapted from the information on http://www.jpl.nasa.gov/releases/2004/138.cfm.

(Added 05/31/04) On Thursday of last week, the Mars Exploration Rover (MER) Opportunity began what controllers expect to be frequent use of an overnight "deep sleep" mode that is designed to conserve energy. Opportunity has managed only 1-2 hours of activity in recent days while it has been examining the stadium-sized Endurance Crater that it arrived at a few weeks ago. Shutting down more completely overnight will conserve enough battery power to add several hours of science operations during the day, according to Jim Erickson, MER deputy project manager at NASA's Jet Propulsion Laboratory in Pasadena, CA.

The deep sleep mode does have a risk - without an overnight heater running, one of the six scientific instruments might be disabled by the cold. This instrument is Opportunity's miniature thermal emission spectrometer - Mini-TES for short. It takes infrared observations that are used to identify minerals from far away to help the science team decide where to send the rover. Its observations also provide close-up evaluation of rock and soil targets, as well as thermal information about surface materials.

As Mars' winter advances in the southern hemisphere and dust continues to accumulate on the solar panels, the amount of electricity the rovers can generate is decreasing. The decline is more serious for Opportunity because the robotic arm of that rover has a heater with a malfunctioning switch that cannot be turned off. The amount of energy wasted was not enough to prevent Opportunity from succeeding in its primary mission, but it is now taking about 1/3 of the rover's diminished amount of solar-generated energy.

While engineers are worrying about this, they are also trying to figure out how well Opportunity would be able to climb out of Endurance Crater if they have it enter the hole.

Spirit, on the other side of Mars, resumed normal operations on May 23 after engineers diagnosed a software glitch that halted the rover's activities on May 21. The symptoms resembled a problem seen about a week earlier where the computer encountered a conflict between two onboard tasks. However, the errors are understood and the two incidents are unrelated. If they recur, neither pose a threat to the rover's health. Spirit is now less than 700 m (0.4 miles) from the base of the Columbia Hills, having traveled more than 2.5 km (1.5 miles) since landing. Controllers are optimistic that Spirit will reach the base of the hills by mid-June.

Adapted from the information on http://www.jpl.nasa.gov/releases/2004/132.cfm.

(Added 05/31/04) The European Space Administration (ESA), after much delay, launched its comet-chasing spacecraft Rosetta on March 2, 2004. Now, the craft has completed its first scientific activity - the observation of comet C/2002 T7, more commonly known as LINEAR.

Linear is currently traveling for the first - and only - time through the inner solar system, and as such it offered Rosetta an excellent opportunity to make its first scientific studies. On April 30, the OSIRIS camera system took images of the comet, and later that day, three more instruments were activated to take more measurements of the comet. The craft studied both the comet's coma and tail in wavelengths ranging from UV to microwave.

Rosetta successfully measured the presence of water molecules in the comet's coma. Detailed analysis of the data will require the complete calibration of the instruments on Rosetta, which will take place in the coming months. The OSIRIS camera produced high-resolution images of the comet at a distance of about 95 million km (59 million miles). The image to the right was taken in blue light and shows the nucleus and a section of the tail that extends about 2 million km (1.2 million miles).

Adapted from the information on http://www.esa.int/export/esaCP/Pr_29_2004_p_EN.html.

(Added 05/21/04) Observations with the Very Large Telescope Interferometer (VLTI) at the ESO Paranal Observatory in Chile have now made it possible to obtain a clear picture of the immediate surroundings of the black hole at the center of an active galaxy. The new results are of the spiral NGC 1068, located about 50 million light-years from Earth.

The observations show a configuration of relatively warm dust (50 °C) approximately 11 light-years across and 7 light-years thick. An inner, hotter zone at about 500 °C is about 2 light-years wide. The observations confirm the current theory that black holes at the centers of active galaxies are surrounded by a thick doughnut-shaped structure of gas and dust.

Due to the combination of light from two 8.2 m telescopes during two observing periods, a maximum resolution of 0.013 arcsec was achieved, which is about 3 light-years at the distance of NGC 1068. Infrared spectra of the central area of the galaxy indicate that the heated dust is probably an alumino-silicate composition.

Adapted from the information on http://www.eso.org/outreach/press-rel/pr-2004/pr-10-04.html.

(Added 05/21/04) With the primary missions of both Spirit and Opportunity completed, the twin Mars Exploration Rovers (MER) are continuing to do science as they start their extended missions. Spirit is en route to a small mountain range called "Columbia Hills" while Opportunity has arrived at its new target, a crater about 130 m in diameter, named "Endurance Crater."

Opportunity's path to Endurance is pictured on the right. It reached the 132 m (430 ft) wide crater on May 6 and sent back an image of the stadium-sized hole. The journey took approximately six weeks to complete across about a half mile (800 m) of Martian desert. A drastically scaled-down mosaic of the crater is on the lower left.

Multiple layers of exposed rock in the crater may reveal what the environment on Mars was like before the standing body of salty water evaporated to leave evidence in the smaller Eagle Crater. Mosaic image of Endurance Crater This crater at which Opportunity now is exploring, is up to 20 m (66 ft) deep - 10 times deeper than Eagle.

Getting into the crater shouldn't be a problem, for the walls slope at about 18-20°. Getting out of the crater is a different issue, and mission planners do not yet know if they could get the craft out if it were to enter. During the lunar landing missions 30 years ago, it was decided that astronauts were not to explore craters as steep and fresh as Endurance.

Meanwhile, on the other side of Mars, Spirit is still on its way to Columbia Hills where scientists hope to find older rocks than the one on the plain that the rover has found so far. It could reach the edge of the hills by mid-June. The hilly, rock-strewn region it is crossing prevents a rapid traverse, with the rover averaging less than 125 m (400 ft) per day. Spirit's route is shown on the right.

Adapted from the information on http://www.jpl.nasa.gov/releases/2004/113.cfm, http://www.jpl.nasa.gov/releases/2004/119.cfm, and http://www.jpl.nasa.gov/releases/2004/125.cfm.

(Added 05/17/04) Pulsars are an extremely dense form of dead star that contains the sun's mass in a volume as wide as Manhattan, and they emit intense beams of energy, often in radio wavelengths. As the star spins, its narrowly confined beams sweep past Earth, creating the pulsing feature that names them. Binary stars are systems where two stars are gravitationally bound and orbit each other about a common center of mass. There is only one known binary pulsar system - where both members of the binary pair are pulsars.

"The physics of radio pulsar emission has eluded researchers for more than three decades," explains Fredrick Jenet of NASA's Jet Propulsion Laboratory in Pasadena, CA. "This system may be the 'Rosetta stone' of radio pulsars, and this model is one step toward its translation."

The discovery of the system, officially named PSR J0737-3039B, was announced in 2003 by a multinational team of researchers. The team originally proposed that the pair was made of one pulsar and one neutron star - a pulsar that does not emit energy as a pulsar does. Later, it was determined that both stars are pulsars, and they were named pulsar A and B. The system is located about 2,000 light-years from us.

Scientists were surprised to discover that the B pulsar is "on" only at certain locations in its orbit - something is turning it on and off. This "something" is closely related to the radio emission beam emanating from the A pulsar. The researchers believe that B becomes bright when it is illuminated by emission from A.

Adapted from the information on http://www.jpl.nasa.gov/releases/2004/114.cfm, and the results were published in the April 29 issue of the journal Nature.

(Added 05/17/04) The Spitzer Space Telescope, an infrared facility in space, was launched less than a year ago and has been gathering data for even less time, but already a treasure trove of its images and spectra has been opened to the public in the Spitzer Science Archive. The data is available for download using an ordinary web browser from the Spitzer home page: http://www.spitzer.caltech.edu.

"We're opening Spitzer's floodgates to the world," explained Dr. Lisa Storrie-Lombardi, deputy manager of the Spitzer Science Center at the California Institute of Technology in Pasadena, CA. "Any astronomer with internet access has this information at his or her fingertips." The Spitzer Science Center is responsible for validating and processing the data into a standard form.

"People can do scientific research by comparing observations made at different wavelengths using data from just the archives," elaborated Spitzer Project Scientist Dr. Michael Werner of NASA's Jet Propulsion Laboratory, Pasadena, CA. "The Spitzer archive will produce scientific surprises for decades long past the observatory's lifetime."

The archive includes data from the 110-hour "first-look" survey of the mid-infrared sky and information from the Spitzer Legacy Science Program - a half dozen scientific investigations that can be used as the basis for future research.

Adapted from the information on http://www.jpl.nasa.gov/releases/2004/121.cfm.

(Added 04/25/04) The European Southern Observatory's Very Large Telescope (VLT) has returned new images of unsurpassed clarity of the surface of Saturn's largest moon, Titan. The mysterious moon, shrouded in a thick orange haze, and its surface is invisible to visual light.

The VLT peered through a narrow, unobscured near-IR spectral window in Titan's dense methane atmosphere and an adjacent non-transparent waveband, making the images virtually uncontaminated by atmospheric components.

The images show a number of various surface regions with very different reflectivity. Of particular interest to planetary geologists are several large dark areas of uniformly low reflectivity. One interpretation of this is that they represent huge surface liquid oceans of hydrocarbons - probably ethane.

This information will be used to target the Huygens probe that will enter Titan's atmosphere later this year, delivered by the Saturn orbiter Cassini that will arrive to the Saturnian system on July 1, 2004.

Adapted from the information on http://www.eso.org/outreach/press-rel/pr-2004/pr-09-04.html.

(Added 04/24/04) The Hubble Heritage Team has released a second image for April of a Lindsay-Shapley ring galaxy, AM 0644-741. 300 million light-years from us, the galaxy lies in the constellation Dorado; this image covers approximately 3 arcminutes across (260,000 light-years). The image was originally taken on January 16/17, 2004, for a total exposure time of 2.8 hours.

This object was once a normal spiral galaxy, like our own Milky Way. Now, a ring of bright, blue stars can be seen wrapped around a yellow nucleus. This galaxy, resembling a sapphire-encrusted bracelet, is being released to commemorate the 14^th anniversary of Hubble's launch on April 24, 1990 and its deployment from the space shuttle Discovery on April 25, 1990.

The ring itself is 150,000 light-years in diameter, making it larger than our galaxy. It is classified as a ring galaxy; ring galaxies are a striking example of how collisions between galaxies can dramatically change their structure while also triggering the formation of new stars. This particular type of collision arises from the intruder galaxy passes directly through the disk of the target galaxy. In this image of AM 0644-741, the galaxy that did the damage is not visible; it can be seen in wider-angle images. The yellow spiral galaxy that is in the upper left corner is a galaxy that belongs to the same group, but it is not interacting.

The shock that arises from the collision drastically alters the orbits of stars, gas, and dust in the target galaxy's disk, sending them outward. The shockwave compresses the gas, creating an intense wave of star formation in its wake. This is why the ring is so blue - it is glowing with the young, large, blue stars that have formed from this. Yet more evidence of star formation are the pink regions of the ring, which are areas of glowing hydrogen gas, fluorescing because of the strong ultraviolet light from the newly formed massive stars.

Adapted from the information on http://heritage.stsci.edu/2004/15/.

(Added 04/16/04) Astronomers have had evidence for supermassive black holes - weighing in at over 10,000 times the mass of the sun to several million times as much - as well as stellar-mass black holes - weighing a few times that of our sun. They also have well-tested models for the formation of such beasts. Evidence in recent years points to the existence of intermediate black holes - weighing a few hundreds to thousands of suns - but the way to form these has remained a mystery.

Observations with NASA's Chandra X-ray Observatory dating back to 2001 indicated the existence of a black hole with a mass of about 1000 suns in a star cluster MGG11 in the starbursting galaxy M82. Simulations on the world's fastest computer, the GRAPE-6 system in Japan, have resolved the mystery of the black hole's formation through the use of two independent models that give the same result.

Researchers used the supercomputer to model individual stars in clusters with up to 600,000 stars each, calculating the orbits and evolution of each star individually. They were able to reproduce the observed characteristics of the star cluster MGG11. And, their simulations resulted in a black hole with a mass of 800-3000 times that of the sun embedded in the cluster.

The simulations showed that if the stellar densities exceed a million times the density of stars in our neighborhood (approximately 0.043 stars per cubic parsec), collisions between stars would dominate the further evolution of the star cluster. Stars would experience repeated collisions with each other, resulting in a runaway effect in which a single star would grow to an enormous size. After the star died, it would collapse into a black hole about 1000 times the mass of the sun.

Adapted from the press releases at http://chandra.harvard.edu/press/04_releases/press_041004.html, and the results are published in the April 15 edition of Nature.

(Added 04/16/04) Extra solar planets were first discovered in 1995, and since then over 120 have been found. The main method has been to detect the planet's subtle effects on its host star by pulling it from side-to-side over the course of its orbit, making it wobble.

Another method of detection relies upon the planet passing in front of the parent star, called transiting, which will cause the star's light output to dim very slightly. This is much harder to observe and much rarer an event, for it requires the planet and star to line up when viewed from Earth.

This method can receive a boost from a natural magnifying glass if the host star lies behind another star. The foreground star can act as a magnification agent, boosting the light output of the star behind it in what is called a gravitational lens. When this happens with stars, it is referred to as microlensing.

What is special about this event is that the star doing the lensing is the one with the planet. The background star was magnified but there were periodic blips of extra brightness, and these spikes indicated a second object. Through analysis of the light curve, it was determined the second object had a mass about 0.4% the mass of the larger object.

The newly discovered system is 17,000 light-years away in the constellation Sagittarius, in the direction of the heart of our galaxy. The planet orbits a red dwarf star, and is estimated to weigh about 1.5 times Jupiter. The planet lies about three times farther from its parent star than Earth does from the sun, and they magnified a star 24,000 light-years away.

Adapted from the press releases at http://www.jpl.nasa.gov/releases/2004/103.cfm.

(Added 04/15/04) The farthest-known solar system object, unofficially named Sedna, was discovered last month. At that time, it was determined that the length of a day on Sedna was approximately 40 Earth days. Nearly all objects in the solar system that do not have a moon rotate much more quickly, so it was believed that Sedna possessed one to slow its revolution. New images of Sedna from the Hubble Space Telescope (HST) have reveled no moon, adding more questions about this distant object.

35 images were taken of Sedna with HST, and none show a companion. HST is the only optical telescope that would be able to separate Sedna from its moon in an image. This unexpected result might offer new clues to the origin and evolution of objects on the far edge of the solar system.

The HST images were unable to resolve Sedna into a disk, placing an upper limit on its size at 1,000 miles across, or about 75% the diameter of Pluto. There is a very small chance that a satellite does exist, but that it was behind or in front of Sedna when the images were taken on March 16.

Adapted from the press releases at http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/14/.

(Added 04/15/04) Meteorites, rocks that survive the fiery journey through Earth's atmosphere, are clues to what lies beyond the Earth. Thousands of meteorites are known, and almost all are believed to originate from asteroids. A few are believed to have lunar origins. Then, there is a small sub-group called SNCs - named for the three main meteorite types in the group - that are believed to have Martian origins. NASA's Mars Exploration Rover Opportunity has now found a rock on Mars that very closely resembles the S type of supposed-Martian meteorites, adding a major boost to the evidence that these are from Mars.

The rock, nicknamed "Bounce," has a spectrum that very closely matches the Shergotty type of Martian meteorite. Shergotty was found in India in 1865 and meteorites that closely resemble it are named shergottites. Two of the approximately twenty known Martian meteorites are shergottites.

The Bounce rock appears to have been ejected from a crater approximately 20 km (16 miles) wide and about 50 km (31 miles) southwest of Opportunity.

Adapted from the press releases at http://www.jpl.nasa.gov/releases/2004/104.cfm.

(Added 04/15/04) NASA's Spitzer Space Telescope, an infrared facility located in solar orbit that is the last of NASA's "Great Observatories" program, has returned a stunning picture of bright, heavy stars that are invisible to all optical telescopes. The violent region of star birth lies hidden behind a veil of dust that blocks visible light, reemitting it in the infrared.

The biggest stars in the region are estimated to be 100,000 times as bright as the sun. The stars are emitting so much radiation that they are tearing apart their nebular surroundings.

The region is called DR21, and it is located about 10,000 light-years away in the Cygnus constellation. The image shows, in false colors, a dense region of massive stars surrounded by a wispy cloud of gas and dust. Red filaments in the area contain organic compounds, and a green jet of gas shooting downwards past the bulge of stars is a fast-moving, hot gas stream that is being ejected from the region's biggest star.

Below DR21, distinct pockets of star formation can be seen, captured in details never before seen. A bubble-like void in the image was possibly excavated by the previous generation of stars.

Adapted from the press releases at http://www.jpl.nasa.gov/releases/2004/100.cfm.

(Added 04/10/04) NASA's Jet Propulsion Laboratory built each of the Mars Exploration Rovers (MERs) to last for at least a 90-day prime mission. Both are functioning well and could operate for several additional months. As a consequence, NASA has officially extended their missions for up to five more months, through September, providing $15 million more for operation costs (a <2% additional investment). Beginning two weeks ago, the team controlling the MER craft Spirit switched from Martian time to Earth time, which will be easier to maintain in the long-term. Controllers for MER Opportunity switched over last week.

The MER Opportunity has found more evidence that water once flowed over Mars' surface. The rocks that Opportunity has examined indicate that the area might be the former shoreline of a salty sea. Clues do not tell how long ago or for what period of time the water covered the area; to gather more information, Opportunity will travel across a plain toward a thicker exposure of rocks in the wall of a crater.

The evidence so far comes from bedding patterns of finely layered rocks that indicate sand-sized grains of sediment formed them, shaped into ripples by water at least 5 cm (2 in.) deep, and flowing at a speed 10-50 cm/sec (4-20 in./sec). The patterns are called crossbedding and festooning, meaning that some layers within the rock lie at right angles to the main layers. Festooned layers have smile-shaped curves produced by shifting of the loose sediments' rippled shapes under a current of water. Other evidence is from finding chlorine and bromine in the rocks.

On the other side of the planet, Opportunity's twin rover, Spirit, is beginning a new phase of its mission which will last into its extended mission program. A range of mountains, named the "Columbia Hills" in dedication to the shuttle astronauts who died on February 1, 2003, is the destination of the tiny rover. The range is an island of older rock surrounded by a younger volcanic layer which surfaces the plain that Spirit has been investigating since it landed in January. Investigators hope that the older rock will hold more clues as to the water on Mars in the past. The drive to the mountains will not be continuous, but will rather feature extended driving with pauses along the way for "traverse science." The trip will cover a distance of 2.3 km (1.3 miles), and it will take Spirit 60-90 Martian days.

Spirit officially began its extended mission on April 6, after it had operated for 90 days and had exceeded 600 meters (1969 ft) of total drive distance.

The extended missions of the rovers include several new goals: Continue atmospheric studies, calibrate and validate data from Mars orbiters for additional types of rocks and soils, travel more than a km to demonstrate mobility technologies, characterize solar array performance over long durations of dust deposition, and demonstrate long-term operation of two mobile science robots on a distant planet.

Adapted from the press releases at http://www.jpl.nasa.gov/releases/2004/90.cfm, http://www.jpl.nasa.gov/releases/2004/92.cfm, http://www.jpl.nasa.gov/releases/2004/97.cfm.

(Added 04/10/04) 30 years ago in 1974, astronomers discovered a mysterious object in the center of the Milky Way, an object that was later found to surround a massive black hole nearly 4 million times the sun's mass and called Sagittarius A* (pronounced "A-star"). An international team of astronomers has finally succeeded in directly measuring the size of this circuitous object, a measurement representing the closest telescopic approach to a black hole so far.

The Milky Way's center, about 26,000 light-years from Earth, is obscured by dust, so visible light cannot be used to study the object. Radio waves penetrate the dust, but they are scattered by turbulent plasma in the space between it and us. The National Science Foundation' Very Long Baseline Array (VLBA) has been able to bring the light into focus for the first time.

The bright, radio-emitting object would fit just inside Earth's orbit about the sun. The black hole itself would fit easily inside Mercury's orbit, the object being only 14 million miles across. These measurements were made after observing the object many times, keeping only the best data, and mathematically removing the scattering effect of the plasma.

Adapted from the press release at http://www.nrao.edu/pr/2004/sagastar/, and the results are published in the April 1 edition of Science Express.

(Added 04/10/04) We reside in the Milky Way galaxy, making it the closest galaxy to us, and yet we know so very little about it because of this proximity. We cannot view the center because of dark lanes of obscuring dust, we cannot image its overall shape because we cannot reach a vantage point above it. We can barely see features half-way across it, let alone accurately determine the three-dimensional shape of our local neighborhood. Now, the results of a 15-year-long survey by a Danish-Swiss-Swedish research team are providing some answers to how the stars around our sun formed.

The team spent 1001 observing nights at the Danish 1.5-m telescope of the European Southern Observatory in Chile and the Swiss 1-m telescope in France. Additional observations were made at the Harvard-Smithsonian Center for Astrophysics in the USA. over 14,000 sun-like stars were observed at an average of 4 times each. This monumental undertaking has provided the distances, ages, chemical analysis, space velocities, and the orbits in the general rotation of the Milky Way of the stars, as well as identified fully 1/3 of them to be double or multiple star systems.

The image on the right shows an artist's view of the observed group of stars orbiting the galaxy with the sun, as seen by an imaginary observer outside the galaxy. The sun's orbit is shown, and for clarity, the stars surrounding the local area have been removed.

The team's initial analysis shows that objects like molecular clouds, spiral arms, black holes, and maybe the central bar of our galaxy have stirred up the motion of stars throughout the entire history of the Milky Way's disk. This shows that the evolution of our galaxy is more complex and chaotic than traditional, simplified models have assumed.

Adapted from the press release at http://www.eso.org/outreach/press-rel/pr-2004/pr-08-04.html, and the results will be published in the journal Astronomy & Astrophysics under the title "The Geneva-Copenhagen survey of the Solar neighbourhood: Ages, metallicities and kinematic properties of ~14,000 F and G dwarfs."

(Added 04/10/04) Mars' polar ice caps are constructed of spiral-like features of canyons, spiraling from both poles over hundreds of miles. No other planet has such structures - first seen by the Viking spacecraft in 1976, and their formation had remained a mystery until now. A new model of formation suggests that periodic heating and cooling are alone sufficient to form the patterns.

Previous explanations had focused upon alternating melting and freezing cycles as well, but they also required wind or shifting ice. "I applied specific parameters that were appropriate to Mars and out of that came spirals that were not just spirals, but spirals that had exactly the shape we see on Mars," described Jon Pelletier, an assistant professor of geosciences at the University of Arizona in Tucson. "They had the right spacing, they had the right curvature, they had the right relationship to one another."

Temperatures on Mars are below freezing most of the year, but during brief periods of the summer, the polar ice caps can get warm enough to let the ice melt a little. Pelletier proposes that during this warmer time, cracks or nicks in the ice's surface that present a steep side toward the sun melt a bit, deepening and widening the crack, allowing heat from the sun to diffuse through the ice, vaporizing it rather than becoming liquid water. The water vapor hits the cold, shady side of the canyon, and this causes it to refreeze, expanding and deepening the canyon.

Adapted from the press release at http://uanews.org/cgi-bin/WebObjects/UANews.woa/5/wa/SRStoryDetails?ArticleID=8860, and the results are published in the April issue of the journal Geology under the title "How do spiral troughs form on Mars?".

(Added 04/10/04) On January 5 of this year, a very rare event occurred: Saturn's moon Titan eclipsed the Crab Nebula. Titan is the largest moon of Saturn, and it is the only moon in the solar system to possess a thick atmosphere. The Crab Nebula is a supernova remnant from a stellar explosion that occurred in A.D. 1054 with an x-ray-bright pulsar at its heart. When Titan eclipsed part of the nebula, it blocked part of the nebula's light, allowing the first x-ray measurements of the large moon with NASA's Earth-orbiting Chandra X-ray Observatory.

"This may be the first transit of the Crab Nebula by Titan since the birth of the Crab Nebula," said Koji Mori of Pennsylvania State University, lead author of an Astrophysical Journal paper describing the results. "The next similar conjunction will take place in 2267, so this was truly a once in a lifetime event."

Chandra was used to show the diameter of the x-ray shadow cast by Titan. It was larger than the diameter of its solid surface, resulting in a measurement of about 550 miles for the height of the x-ray absorbing region of Titan's atmosphere. This is slightly larger than that implied by Voyager 1 observations in radio, infrared, and ultraviolet wavelengths made in 1980. The closer proximity to the sun of Saturn in 2003 might account for the atmospheric expansion.

Understanding the extent of Titan's atmosphere is very important to the planning of the Cassini-Huygens mission to Saturn and Titan. Voyager 1 had only measured the atmosphere to heights below 300 miles and above 600, so the intermediate region remained a mystery until this observation. If the atmosphere has really expanded, then the planned trajectory of the probes may need to be changed.

Adapted from the press release at http://chandra.harvard.edu/press/04_releases/press_040504.html, and the results will appear in the Astrophysical Journal in June 2004.

(Added 04/10/04) The Hubble Heritage Team has released April's image of the spiral galaxy NGC 300. 6.5 million light-years from us, the galaxy lies in the constellation Sculptor; this image covers approximately 3 arcminutes across (5,600 light-years). The image was originally taken on July 19 and September 28, 2002, for a total exposure time of 2 hours.

Countless stars can be seen in the center of the nearby galaxy NGC 300. Hubble's position, high above the blurring effects of Earth's atmosphere, provide unprecedented clarity in the image of this galaxy, despite the millions of light-years between us and it. Previous ground-based images could only resolve a few bright stars.

NGC 300 is a spiral galaxy similar to our own Milky Way. It is a member of a nearby group of galaxies known as the "Sculptor Group" - named for the constellation in which it is observed. Its distance makes it one of the closest neighbors to our galaxy.

The color composite was made from images taken in blue, green, and infrared light. Hot, young blue stars appear in clusters in the galaxy's spiral arms. Ribbons of dark red stars mark sheets of dust that shield the stars behind them. Near the image's center is the galaxy's nucleus - the bright, compact center of the galaxy.

The images were taken to test a new method for measuring distances to galaxies and comparing it to the distance measurements that have traditionally been used. Distances to astronomical objects is one of the most active areas of astronomy, and it has remained a perpetual problem. The new, experimental method uses the very luminous blue stars along with other information such as temperature, surface gravity, and mass outflow, in order to measure the distances to the stars.

Adapted from the information on http://heritage.stsci.edu/2004/13/.

(Added 03/20/04) The Mars Exploration Rover (MER) Opportunity has further explored the evidence of water existing on ancient Mars. It has been exploring the "blueberry" features near its landing site lie embedded in an outcrop of rocks and are scattered over some areas of soil. Individual spherules are too small to analyze with the rover's tools, but groups of them can. The analysis shows that the berries contain large amounts of an iron-bearing mineral called "hematite" that, on Earth, usually forms in a wet environment. The position, concentration, and size of the spherules points to their forming in water-soaked deposits.

Meanwhile on the other side of Mars, Opportunity's twin, Spirit, completed its 335-meter (1099-ft) trek to the crater "Bonneville." Images sent back show the interior of the crater as well as its far rim, which lies about two football fields away - about 10 times the diameter of Opportunity's landing site crater. Initial images do not show any obvious layers in the crater's inner wall, but they show clues of rock features high on the far side. For the past and over the next several days, mission scientists will continue to explore the crater with Spirit's armada of instruments, and they may or may not send Spirit into the crater itself.

Adapted from the press releases at http://www.jpl.nasa.gov/releases/2004/88.cfm and http://www.jpl.nasa.gov/releases/2004/83.cfm.

(Added 03/19/04) In what is the closest call in known history, a Near-Earth Asteroid (NEA) that was discovered Monday (March 15) night passed only 43,000 km (26,500 miles) above our planet's surface on Thursday, March 18 at 22:08 UTC.

The NEA, designated 2004 FH, is approximately 30 m (100 ft) in diameter. On average, objects this size are estimated to pass within this distance about once every two years, but they all have gone by undetected. The only unusual feature about this is that it was found. The distance above Earth that it passed was well within the moon's orbit, and only 3.4 Earth diameters away. Earth's gravity bent the asteroid's orbit by about 15°.

The asteroid could be seen using a pair of good binoculars from areas of Europe, Asia, and most of the Southern Hemisphere. Scientists used the unprecedented opportunity to study a small NEA up close.

Adapted from the press release at http://www.jpl.nasa.gov/releases/2004/2004-FH.cfm.

(Added 03/19/04) In grade school, children are usually taught that the solar system consists of nine planets and a central star; sometimes they are lucky and are taught about the asteroid belt and comets. If someone is ambitious and tries to learn more, they find that the solar system is not so clear-cut and simple, but it is littered with more space debris, and that it has a theorized large belt of asteroids and comets out beyond Pluto, called the Kuiper Belt. Even beyond the Kuiper Belt, astronomers have theorized that there exists a region of comets called the Oort Cloud that might stretch up to two light-years from the sun, and could explain the orbits of certain comets.

NASA-funded researchers have now discovered what is the most distant (currently known) object to orbit the sun. It lies three times farther from the sun than Pluto at about 13 billion km (8 billion miles). It is presently being called "Sedna" for the Inuit goddess of the ocean. The discovering scientists believe that it could be the first Oort Cloud object found.

Sedna lies in the coldest known region of the solar system where temperatures never rise above -240 °C (-400 °F). The "planetoid" is actually near its closest approach to the sun in its 10,500-year orbit. The farthest point in its orbit is about 130 billion km (84 billion miles) from the sun, which is about 900 times farther from the sun than Earth. The image on the right shows the orbits of various bodies in the solar system to scale.

Sedna - Size Comparisons Sedna is estimated to be approximately 75% the size of Pluto (see image to the left for size comparisons). NASA's Spitzer Space Telescope was unable to detect the heat from the cold body, placing its size at less than 1700 km (1000 miles). This makes Sedna the largest object in the solar system that has been found since Pluto's discovery in 1930.

Other than Mars, it is the reddest object in the solar system - a feature that has yet to be explained. Yet another yet-unexplained feature of Sedna is the highly elliptical orbit that it occupies. It is because of this far-reaching orbit that it could be a member of the Oort Cloud. However, Sedna lies ten times closer than the predicted distance of the Oort Cloud.

A possible explanation is that it could be a member of an "inner Oort Cloud" that would have formed by gravity from a rogue star near the sun in the early history of the solar system. If the star passed close enough, it would have dislodged comets from the Oort Cloud, leading to an intense barrage of comets flung into the inner solar system. Other comets that did not get as strong a nudge would have formed this inner Oort Cloud.

There is indirect evidence that Sedna has a moon - it is hoped that NASA's Hubble Space Telescope can detect it if it exists. Over the next 72 years, Sedna will come closer and become brighter before it heads back into the farther reaches of the solar system.

Adapted from the press release at http://www.jpl.nasa.gov/releases/2004/85.cfm.

(Added 03/19/04) The Sloan Digital Sky Survey (SDSS) - a multi-year international effort to map 1/4 of the sky - has released one of the largest astronomy catalogs ever compiled to the public: A whopping 6 TB of data (6,000,000 megabytes). The data release, the second from SDSS, is made of both photometric and spectroscopic observations from the last two years.

The release provides digital images and measured properties of over 88 million objects, as well as spectra and redshifts of over 350,000 objects. The data are available from both the SDSS web site and the SkyServer web site - the later being more appropriate for the general public.

Adapted from the press release at http://www.sdss.org/news/releases/20040315.datarelease2.html.

(Added 03/10/04) The deepest image of the universe ever seen has been taken with the Hubble Space Telescope; it is called the Hubble Ultra Deep Field (HUDF). The exposure was taken over about one million seconds. The image here is only a small portion of the full field.

It reveals the first galaxies to emerge from the "dark ages" - the time shortly after the Big Bang when the first stars reheated the cold, dark universe. The image at the right is a small portion of the field. The full field is made of two separate images, one taken by the Advanced Camera for Surveys and the other by the Near Infrared Camera and Multi-object Spectrometer. Both show galaxies too faint to be seen from the ground, or even in Hubble's previous Deep Fields from 1995 and 1998.

The HUDF field contains an estimated 10,000 galaxies. In ground-based images, the patch of sky in which the galaxies reside (just one-tenth the diameter of the full moon) is largely empty. Located in the constellation Fornax, the region is below the constellation Orion. The final ACS image, assembled by Anton Koekemoer of the Space Telescope Science Institute, is studded with a wide range of galaxies of various sizes, shapes, and colors. In vibrant contrast to the image's rich harvest of classic spiral and elliptical galaxies, there is a zoo of oddball galaxies littering the field. Some look like toothpicks; others like links on a bracelet. A few appear to be interacting. Their strange shapes are a far cry from the majestic spiral and elliptical galaxies we see today. These oddball galaxies chronicle a period when the universe was more chaotic. Order and structure were just beginning to emerge.

Adapted from the press release at http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/07/.

(Added 03/10/04) The idea of a watery Mars has existed for well over 100 years. We have since concluded that Mars contains no regions of surface water - in fact the temperature and pressure on the surface of Mars are such that liquid water cannot form - but the idea of water being just a few meters under the surface or the idea of a warm and wet Mars in the past has been much harder to prove or disprove.

One of the primary goals of the Mars Exploration Rover (MER) program has been to determine whether, at some time in the past, Mars possessed areas of standing water. The MER Opportunity has now verified that it is in a region that was soaking wet in the past. Evidence the rover found in a rock outcrop led to the conclusion; its composition as well as the physical appearance helped make the case for a watery history.

"Liquid water once flowed through these rocks. It changed their texture, and it changed their chemistry," said Dr. Steve Squyres of Cornell University, Ithaca, NY, principal investigator for the science instruments on Opportunity and its twin, Spirit. "We've been able to read the tell-tale clues the water left behind, giving us confidence in that conclusion," he said.

Opportunity has more work ahead. It will try to determine whether, besides being exposed to water after they formed, the rocks may have originally been laid down by minerals precipitating out of solution at the bottom of a salty lake or sea. The robotic field geologist has spent most of the past three weeks surveying the whole outcrop, and then turning back for close-up inspection of selected portions. The rover found a very high concentration of sulfur in the outcrop with its alpha particle x-ray spectrometer, which identifies chemical elements in a sample. "The chemical form of this sulfur appears to be in magnesium, iron or other sulfate salts," said Dr. Benton Clark of Lockheed Martin Space Systems, Denver. "Elements that can form chloride or even bromide salts have also been detected."

At the same location, the rover's Moessbauer spectrometer, which identifies iron-bearing minerals, detected a hydrated iron sulfate mineral called jarosite. Germany provided both these instruments. Opportunity's miniature thermal emission spectrometer has also provided evidence for sulfates. On Earth, rocks with as much salt as this Mars rock either have formed in water or, after formation, have been highly altered by long exposures to water. Jarosite may point to the rock's wet history having been in an acidic lake or an acidic hot springs environment.

Pictures from the rover's panoramic camera and microscopic imager reveal the target rock, dubbed "El Capitan," is thoroughly pocked with indentations about a centimeter (0.4 inch) long and one-fourth or less that wide, with apparently random orientations. This distinctive texture is familiar to geologists as the sites where crystals of salt minerals form within rocks that sit in briny water. When the crystals later disappear, either by erosion or by dissolving in less-salty water, the voids left behind are called vugs, and in this case they conform to the geometry of possible former evaporite minerals.

Round particles the size of BBs are embedded in the outcrop. From shape alone, these spherules might be formed from volcanic eruptions, from lofting of molten droplets by a meteor impact, or from accumulation of minerals coming out of solution inside a porous, water-soaked rock. Opportunity's observations that the spherules are not concentrated at particular layers in the outcrop weigh against a volcanic or impact origin, but do not completely rule out those origins. Layers in the rock that lie at an angle to the main layers, a pattern called crossbedding, can result from the action of wind or water. Preliminary views by Opportunity hint the crossbedding bears hallmarks of water action, such as the small scale of the crossbedding and possible concave patterns formed by sinuous crestlines of underwater ridges.

The images obtained to date are not adequate for a definitive answer. So scientists plan to maneuver Opportunity closer to the features for a better look. "We have tantalizing clues, and we're planning to evaluate this possibility in the near future," Grotzinger said.

Several days later, the same rover made another first - it observed eclipses of the sun from Mars by both of its moons, Deimos and Phobos. In the 1970s, the Viking landers observed the shadow of of the moon Phobos moving across the landscape; in 1997, the Mars Pathfinder saw Phobos emerge from a lunar eclipse - from Mars' shadow.

Scientifically, eclipse observations can help refine the orbits and orbital evolution of the moons. Depending on the orientation of Phobos as it passes in front of the sun, the images could also add new information about the shape of the moon.

The rovers' panoramic cameras observe the sun nearly every martian day as a way to gain information about how Mars' atmosphere affects the sunlight. The challenge for the eclipse observations is in the timing. Deimos crosses the sun's disc in only about 50 to 60 seconds. Phobos moves even more quickly, crossing the sun in only 20 to 30 seconds.

From Earth, our moon and the sun have the appearance of almost identically sized discs in the sky, so the moon almost exactly covers the sun during a total solar eclipse. Because Mars is farther from the sun than Earth is, the sun looks only about two-thirds as wide from Mars as it does from Earth. However, Mars' moons are so small that even Phobos covers only about half of the sun's disc during an eclipse seen from Mars.

Adapted from the press releases at http://www.nasa.gov/home/hqnews/2004/mar/HQ_04077_water_on_mars.html and http://www.nasa.gov/home/hqnews/2004/mar/HQ_04085_rovers_solar_eclipses.html.

(Added 03/10/04) The Hubble Heritage Team has released March's image of the nova-like variable star and surrounding light echo V838 Monocerotis (V838 Mon). 20,000 light-years from us, V838 Mon lies in the constellation Monoceros; this image covers approximately 2.4 arcminutes across (13.6 light-years). The image was originally taken on February 8, 2004, for a total exposure time of 1.8 hours.

The image is a composite of three filters (blue, visible, and infrared) taken with the Advanced Camera for Surveys. It shows the latest view of an expanding halo of light around the distant star. The illumination of interstellar dust comes from the red supergiant star at the middle of the image, which gave off a flashbulb-like pulse of light two years ago.

The expanding illumination is of a dusty cloud around the star - called a "light echo" - and it has been revealing remarkable structures ever since the star suddenly brightened for several weeks in early 200. Hubble has followed the light echo since, and the new image shows swirls in the dusty cloud for the first time.

The eddies are probably caused by turbulence in the dust and gas around the star as they slowly expand away. They were likely ejected from the star in a previous explosion, similar to the 2002 event, probably dating back tens of thousands of years ago. It was invisible and unexpected until the explosion two years ago.

The January 2002 event brightened the star, causing it to become 600,00 times more luminous than the sun. This caused it to become one of the most bright stars in the entire Milky Way, until it faded away four months later in April 2002.

Adapted from the information on http://heritage.stsci.edu/2004/10/.

(Added 03/10/04) The Rosetta comet probe, funded by the European Space Administration (ESA), was launched at 07:17 GMT on March 2. The probe should reach its target, comet 67 P/Churyumov-Gerasimenko, in 2014 after three Earth and one Mars flyby. It will pass by at least one asteroid on its trip.

Rosetta is the first probe ever designed to enter orbit about a comet's nucleus and release a lander onto its surface. It is scheduled to conduct a thorough study of the comet for over a year.

Rosetta was launched on a European Ariane 5 launch vehicle at the Guiana Space Centre, Europe's spaceport in Kourou, French Guiana. The launcher placed the upper stage and payload into a coast orbit of 200x4000 km (122x2440 mile). About two hours later (09:14 GMT) the upper stage ignited its own engine to reach a heliocentric orbit; the probe was released 18 minutes later.

"After the recent success of Mars Express, Europe is now heading to deep space with another fantastic mission. We will have to be patient, as the rendezvous with the comet will not take place until ten years from now, but I think it's worth the wait" said ESA's Director General Jean-Jacques Dordain witnessing the launch from Kourou.

ESA’s Operations Centre (ESOC) in Darmstadt, Germany, has established contact with the probe as it flies away from Earth at a relative speed of about 3.4 km/s. ESOC will be in charge of Rosetta operations and orbit determination throughout the mission. During the next eight months, the spacecraft’s onboard systems will be checked and its science payload will be commissioned.

Adapted from the press release at http://www.esa.int/export/esaCP/Pr_14_2004_p_EN.html.

(Added 03/10/04) NASA's Chandra X-ray Observatory has made the first clear detection of x-rays coming from the planet Saturn. The Chandra image, presented on the right next to an optical image of Saturn taken with the Hubble Space Telescope, shows that the x-rays are concentrated near Saturn's equator - a surprising result because Jupiter's x-rays are concentrated near the poles. Existing theories cannot easily explain the intensity nor distribution of Saturn's x-rays.

The observation took 20 hours in April of 2003. The distribution of x-ray energy is very similar to that of the sun. "This indicates that Saturn's x-ray emission is due to the scattering of solar x-rays by Saturn's atmosphere," claimed Jan-Uwe Ness, of the University of Hamburg in Germany and lead author of a paper discussing the Saturn results in an upcoming issue of Astronomy & Astrophysics. "It's a puzzle, since the intensity of Saturn's x-rays requires that Saturn reflects x-rays fifty times more efficiently than the moon."

The observed 90 MW of x-ray power from Saturn's equatorial region is roughly consistent with previous observations of radiation from Jupiter's equatorial region, suggesting that both planets reflect solar x-rays at unexpectedly high rates. Further Jovian observations are needed to test this. X-rays were not detected from Saturn's rings.

Adapted from the press release at http://chandra.harvard.edu/press/04_releases/press_030804.html.

(Added 02/29/04) Cassini, a spacecraft bound for Saturn since 1997, is fast approaching its quarry, and it will arrive at Saturn on July 1, 2004. It has now sent back what may become a weekly event: A postcard of the ringed planet.

The image was taken on February 9, 2004, at a distance of 69.4 million km (43.2 million miles) - about half the distance from Earth to the sun. The picture was taken from Cassini's narrow angle camera, one of the two cameras the craft has; a series of exposures were taken through different filters to create the full-color image (colors were slightly enhanced during processing).

The smallest features that are visible in the image are about 540 km (336 miles) across. Fine details in the atmosphere and rings that the Voyager probes witnessed are beginning to show through. The tiny moon Enceladus is faintly visible in the upper-left corner of the image; its brightness relative to Saturn's has been enhanced by 700%.

Adapted from the press release at http://www.jpl.nasa.gov/releases/2004/71.cfm.

(Added 02/29/04) The early universe was veiled with a fog of neutral hydrogen and helium. Even the brilliant ultraviolet (UV) light of stars in the first primordial galaxies could barely penetrate the all-absorbing curtains of gas, leading some astronomers to term that era the cosmic "Dark Ages." Only over hundreds of millions of years could those first stars gradually heat and ionize the surrounding gas, transforming an opaque ocean of space into the transparent void of today. Without that transformation, no telescope would be able to see the UV radiation emitted by sources beyond our own galaxy. All our knowledge of UV sources would be confined to the Milky Way.

Determining precisely when that transformation from darkness to light (known as re-ionization) took place - and what caused it - will yield important insights into the history of galaxy formation in the infant universe. New theoretical work by J. Stuart Wyithe (University of Melbourne) and Abraham Loeb (Harvard-Smithsonian Center for Astrophysics), reported in the February 26, 2004, issue of Nature, shows that the cosmic Dark Ages lasted for more than a billion years because the billion-year-old universe was still mostly neutral.

The Big Bang created a universe filled with hot, ionized hydrogen and helium. After about 380,000 years, the universe expanded and cooled enough for electrons and atomic nuclei to recombine, forming UV-absorbing, neutral hydrogen and helium atoms. Transformation from the consequent darkness into now-pervasive transparency required that the gas filling the universe be re-ionized, or once again split into its constituent electrons and nuclei. The question is: When did that re-ionization occur?

"A simple model of instant and complete ionization, using data from the WMAP satellite, implies that re-ionization took place about 200 million years after the Big Bang, around a redshift of 17. However, the actual re-ionization process was not instant and complete. It was more complicated," explained Wyithe.

To draw their conclusion, Wyithe and Loeb studied quasars - very distant and very bright objects that can be seen across billions of light-years of space. Their extreme brilliance means that quasars can be used as cosmic flashlights to illuminate not only their immediate environment, but also all of the intervening space between the quasar and the Earth. At the heart of every quasar lies a supermassive black hole gulping down nearby matter. As matter spirals into the black hole, some of its gravitational energy is converted into light.

Ultraviolet radiation from a quasar will ionize gas in the surrounding intergalactic medium (IGM). While bright quasars were not numerous enough in the early universe to cause widespread re-ionization, each of them was powerful enough to form a local "bubble" of ionized gas. The size of the bubble depends on the properties of the surrounding gas. If the nearby IGM is mostly neutral, the quasar has to work harder to ionize the gas, and can only create a small bubble. An IGM that is already mostly ionized means less work for the quasar and a larger bubble.

To calculate the fraction of neutral hydrogen in the early universe, Wyithe and Loeb used the two most distant quasars known, one at a redshift of z~6.3 and one at z~6.4, corresponding to distances of about 13 billion light-years. They predicted the expected size of the ionized "bubble" around each quasar, assuming reasonable values for the emission rate of ionizing photons and time elapsed (i.e. the quasar's lifetime), and then they compared their predictions to the observed sizes. The conclusion was clear.

"The observed bubble sizes were small - so small that the fraction of neutral hydrogen had to be large, in the range of tens of percent. So, even one billion years after the Big Bang, when re-ionization should have been well underway according to WMAP, most of the intergalactic medium was still neutral," concludes Wyithe.

Adapted from the press release at http://cfa-www.harvard.edu/press/pr0410.html.

(Added 02/22/04) In 1987, a star, about 20 times the mass of the sun, in the Large Magellanic Cloud - a small satellite galaxy of the Milky Way - went supernova, shining with the luminosity of 100,000,000 suns for several months following its discovery on February 23, 1987. Although the supernova itself is now a million times fainter than 17 years ago, a new light show in the space surrounding it is just beginning.

The image on the left was taken on November 28, 2003 by the Advanced Camera for Surveys aboard the Hubble Space Telescope. It shows many bright spots along a ring of gas; these bright balls are being produced as a high-speed shockwave from the initial explosion is plowing into a ring of gas at more than 1,000,000 mph. The collision is heating the gas ring, causing its interior regions to glow.

The first hot spot - the brightest in the image at the 5:00 position - was detected in 1996, but now dozens light the ring. the temperatures in the regions range from a few thousand to a million degrees Fahrenheit. The balls of material cannot be individually resolved from ground-based telescopes - only an orbiting observatory can see them individually.

Over the next few years, astronomers expect the entire ring to become lit as it absorbs the full shockwave. The ring is expected to become luminous enough to show the stars's surroundings, providing astronomers with new information on how the star ejected its outer layers before the explosion nearly two decades ago. The ring is about a light-year across, and it was formed about 20,000 years before the blast.

The elongated and expanding object seen in the middle of the ring is made of debris from the supernova blast. It is glowing because it is heated by radioactive elements, mainly Ti-44, that were created in the explosion. They will continue to glow for many decades.

Adapted from the press release at http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/09/image/a.

(Added 02/22/04) 45 A.U. from the sun, orbiting in over 300 years, and shining at 18.5 magnitude, Kuiper Belt Object (KBO) 2004 DW is about 1400 km in diameter, making it the largest sub-Pluto-sized body found to-date.

The discoverers, Caltech associate professor of planetary astronomy Mike Brown and his colleagues Chad Trujillo (now at the Gemini North observatory in Hawaii), and David Rabinowitz of Yale University, found the KBO as part of the same search program that discovered Quaoar - the previous size record holder - in late 2002.

The object, for now still carrying its temporary designation of 2004 DW, has not been located in old photographic plates, so only one day of its orbit has been observed. Because of this, only its current distance and how its orbit is tilted relative to the planets can be determined (it's tilt is about 20° -- Pluto is tilted 17°). Its size is an estimate that is based upon a comparison of its luminosity with that of Quaoar. If its reflectivity - albedo - is greater, then it is smaller, and if its albedo is smaller than Quaoar's, then the KBO is larger than 1400 km.

Adapted from the press release at http://pr.caltech.edu/media/Press_Releases/PR12495.html.

(Added 02/18/04) A black hole, a type of dead star that has such a strong gravitational field that not even light can escape from it, has been caught in the act of ripping apart a star and eating part of it. The observations come from two orbiting telescopes - the ESA's XMM-Newton and NASA's Chandra X-ray Observatories. The event had long-been predicted but had not yet been seen.

Astronomers believe a star came too close to a giant black hole after being thrown off-course by a close encounter with another star. As it neared the black hole, the star was stretched until it was torn apart. The discovery provides crucial information about how these black holes grow and affect surrounding stars and gas.

Observations from Chandra and XMM-Newton, combined with earlier images from the German Roentgen satellite, detected a powerful x-ray outburst from the center of the galaxy RX J1242-11. This was one of the most extreme outbursts ever detected in a galaxy, and it was caused by gas from the destroyed star that was heated to millions of degrees before being swallowed by the black hole. The energy that was released in the process was equivalent to a supernova.

The black hole in this case is estimated to weigh about 100,000,000 times that of the sun. In contrast, the star that was eaten was probably about the size of our sun. The team of astronomers estimate that about 1% of the star's mass was ultimately consumed by the black hole.

Other large flares have been seen from other galaxies, but this is the first studied with the high-spatial resolution of Chandra and the high-spectral resolution of XMM-Newton. In the future, searches using these and other survey instruments should find many other such events. Detailed studies with future observatories should teach us about the extreme physics around supermassive black holes.

Adapted from the press release at http://chandra.harvard.edu/press/04_releases/press_021804.html.

(Added 02/16/04) Just like anyone else, astronomers like to be able to say that they found the first this or the biggest that. A team of international astronomers may now have bragging rights for finding the oldest galaxy in the universe at an estimated 13 billion light-years away, making it form when the universe was only 750 million years old.

The galaxy was found by combining the Hubble Space Telescope (HST) and the Keck Telescopes (on Mauna Kea in Hawaii). The galaxy is still only visible because of a gravitational lens - a massive cluster of galaxies is in the line of sight to the galaxy in question, and acts to magnify the light from the galaxy behind it. The new galaxy was detected in a long exposure of the nearby cluster of galaxies Abell 2218, taken with the Advanced Camera for Surveys on HST.

The Hubble images show that the object has a redshift of 6.6 to 7.1. Spectrographs from the Keck telescopes suggest that the object has a redshift towards the upper end of this range, around 7.

Adapted from the press release at http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/08/.

(Added 02/16/04) Mars has become a busy place with both orbiting probes and landers on the surface. In the old days, if you sent a probe to another world, you were responsible for its communication. Now, a major leap in communication has been accomplished between the European Space Agency's Mars Express orbiter and NASA's Mars Exploration Rover Spirit.

On February 6, while Mars Express was above the area that Spirit is examining, the orbiter transferred commands from Earth to the rover, and relayed data from the rover back to Earth. "This was the first in-orbit communication between ESA and NASA spacecraft, and we have also created the first working international communications network around another planet," said Rudolf Schmidt, ESA's Project Manager for Mars Express. "Both are significant achievements, two more 'firsts' for Mars Express and the Mars Exploration Rovers." Jennifer Trosper, Spirit Mission Manager at NASA's Jet Propulsion Laboratory, California, USA, said, "We have an international interplanetary communications network established at Mars."

"This is excellent news," said JPL's Richard Horttor, project manager for NASA's roles in Mars Express. "The communication sessions between Mars Express and Spirit were pristine. Not a single bit of data was missing or added, and there were no duplications." This exercise demonstrates the increased flexibility and capabilities of inter-agency cooperation and highlights the close mutual support that is essential when undertaking international space exploration.

Adapted from the press release at http://www.esa.int/export/esaCP/Pr_10_2004_p_EN.html.

(Added 02/16/04) Valentine's Day is generally seen as a day to give candy or flowers to one's sweetheart, or as a sad, depressing day for those that are single - also known as "Singles' Awareness Day." For this year's Valentine's/Singles' Awareness Day, a commemorative image of NGC 7129 has been released, taken with the Spitzer Space Telescope.

A cluster of newborn stars is what creates the glow in this reflection nebula, which lies a distance of about 3300 light-years away in the constellation Cepheus. Approximately 130 young stars lie in the nebula, which contains enough material to create a thousand Sun-like stars, and has a diameter of about the distance between the sun and Proxima Centauri.

"By combining data from the Smithsonian's MMT Telescope in Arizona with Spitzer data, we find that roughly half of these stars are surrounded by disks of gas and dust. Each of these disks is a forming solar system," said researcher Tom Megeath of the Harvard-Smithsonian Center for Astrophysics.

Over the last, brief, million years, the stars within the cloud of dust and gas have blown a large, irregular bubble in the molecular cloud that once contained them like a cocoon. The pink is produced by glowing dust grains on the surface of the bubble and are being heated by the intense light from the embedded young stars. When the dust absorbs ultraviolet and visible light from the stars, they are heated and re-emit the energy in longer, infrared wavelengths that the Spitzer can detect.

Three very young and bright stars near the center of the image are sending out jets of supersonic gas into the surrounding cloud. The impact of the jets heats molecules of carbon monoxide (CO) in the cloud, which has been colored green in this image.

The Spitzer Space Telescope image was obtained with an infrared array camera that is sensitive to infrared light at wavelengths that are about ten times longer than visible light. In this four-color composite, emission at 3.6 µm is depicted in blue, 4.5 µm in green, 5.8 µm in orange, and 8.0 µm in red. The image covers a region that is about one quarter the size of the full moon.

Adapted from the press release at http://cfa-www.harvard.edu/press/pr0406.html.

(Added 02/11/04) The Beagle 2 Management Board at a meeting in London on February 6 declared Beagle 2 lost. It has failed to communicate with any craft or receiver on Earth since it was released from its mother craft. An inquiry board has been established to determine the most likely cause of failure.

Adapted from the press release at http://www.esa.int/export/esaCP/SEMQ5C1PGQD_index_0.html.

(Added 02/07/04) This week has been a busy one for both Spirit and Opportunity rovers, with Spirit relatively back to health and restarting its science data collection, and Opportunity examining soil near its lander.

Mars Exploration Rover (MER) Opportunity - Soil Sample Opportunity examined its first soil patch on February 4 within the crater that it landed. "There are features in this soil unlike anything ever seen on Mars before," pronounced Dr. Steve Squyres of Cornell University in Ithaca, NY - the principal investigator for the science instruments on the two Mars Exploration Rovers (MERs).

The image that was returned (left) shows spherical particles. It was taken with Opportunity's microscopic imager, the last of 20 cameras to be used in the two rover missions. Other particles in the image have jagged shapes. "The variety of shapes and colors indicates we're having particles brought in from a variety of sources," said Dr. Ken Herkenhoff of the U.S. Geological Survey's Astrogeology Team in Flagstaff, AZ.

A new mineral map that was constructed by Opportunity - the first ever done from the surface of another planet - shows that concentrations of coarse-grained hematite vary in different parts of the crater. To get a better look at the hematite, Opportunity went to the area of its highest concentration, driving half-way there on Thursday. On Friday, Opportunity drove almost the rest of the way. It was climbing a slope of about 13°, and it came short by about 0.5 m (1.5 ft), probably due to slippage. It should go the rest of the way on Saturday.

Spirit, meanwhile, went through a procedure to reformat its flash memory - a preventative measure that had been planned, and it was successful. After the reformatting, Spirit - on Thursday - brushed off an area on the rock nicknamed "Adirondack" in order to prepare for a dust-free examination of its surface. Steel bristles on the rover's rock abrasion tool cleaned a circular patch on the rock. Five minutes of brushing resulted in a surface much darker than before - a surprise because the rock had been selected due to its relatively dust-free surface.

On Friday, the rock abrasion tool was used for its primary function - to grind away at the rock's surface with its diamond teeth. Several instruments will now be used to inspect the freshly exposed interior of the rock. This weekend, mission controllers plan to tell Spirit to begin driving again.

Adapted from the press releases at http://www.jpl.nasa.gov/releases/2004/51.cfm, http://www.jpl.nasa.gov/releases/2004/52.cfm, http://www.jpl.nasa.gov/releases/2004/53.cfm.

(Added 02/07/04) The Hubble Heritage Team has released February's image of the spiral galaxy M64, AKA NGC 4826 AKA the Black Eye Galaxy. 17 million light-years from us, M64 lies in the constellation Coma Berenices; this image covers approximately 1.5 arcminutes across (7400 light-years). The image was originally taken on April 8 and July 6, 2001, for a total exposure time of 1.1 hours.

Two galaxies collided to make this months' Hubble Heritage image. The merger left an unusual appearance as well as bizarre internal motions of stars and gas in this spiral galaxy. Fine details of the dark band are revealed in this image of the central portion of M64.

At first glance, this appears to be a fairly normal pinwheel-shaped spiral galaxy. All of the stars are rotating in the same direction, as with most galaxies, clockwise in this image. However, detailed observations in the 1990s led to the remarkable discovery that the gas in the outer regions rotates in the opposite direction as the gas and stars in the inner parts of the galaxy.

Active star formation is occurring in the outer region where oppositely rotating gases collide, are compressed, and contract. Particularly noticeable are the bright blue clusters of stars in the dark dust band, as well as glowing pink areas of stellar nurseries - hydrogen gas that fluoresces when exposed to ultraviolet light from new stars.

Astronomers believe that the oppositely rotating gas arose when M64 absorbed a satellite galaxy that collided with it, maybe 1 billion years ago. The small galaxy is almost completely destroyed, but the tell-tale signs of it lie in the oppositely rotating gas. Four different filters were used to create this color composite.

Adapted from the information on http://heritage.stsci.edu/2004/04/.

(Added 02/07/04) Planets circling around foreign stars, extra-solar planets (exoplanets, for short), were first discovered nearly a decade ago by indirect methods. None have ever been imaged - just detected. Now, an international team of astronomers has for the first time detected oxygen and carbon in the atmosphere of a planet beyond our solar system.

Gaseous hydrogen is flowing out from the planet at nearly the speed of sound, and it is dragging heavier oxygen and carbon up from the lower atmosphere like dust in a whirlwind. The oxygen and carbon surround the planet in an extended envelop, telling scientists that they are seeing a planet "blow off" its atmosphere. Some argue that early Venus and Earth may have lost their original atmospheres by this same mechanism.

The planet is a so-called "hot Jupiter," 150 light-years away, orbiting star HD 209458 in the constellation Pegasus. The system's orientation to Earth allows us to view the planet as it crosses in front of its parent stars, permitting the period of its orbit - 3.5 days - to be determined, and partially eclipsing its star during each 3-hr transit. The data was taken with the Hubble Space Telescope in October and November of 2003, with Hubble's ultraviolet spectrograph. Such observations can only be made from space because our atmosphere blocks out UV light.

The planet's disk eclipses about 1.5% of the star during each transit. However, its large atmosphere covers 8-15% of the star. When the UV spectrum revealed absorption by oxygen and ionized carbon in the atmosphere, the conclusion was that it was produced in an "atmospheric blow off." Team member Jack McConnell of York University, Canada, predicted this phenomenon. He theorized that at the high temperatures of the planet, hydrogen atoms in the upper atmosphere would reach speeds great enough to escape the planet’s gravity, which is comparable to Earth’s gravity. As the hydrogen atoms flowed out from the planet at near sonic speed, they would drag heavier oxygen and carbon atoms in the atmosphere up with them, called blow off.

French team member Alain Lecavelier des Etangs found that the planet is so close to its star that the combined gravity fields of the star and the planet shape its upper atmosphere into the form of a rugby ball, allowing even more gas to escape. The astronomers are reporting the new discovery in a forthcoming issue of Astrophysical Journal Letters (ApJ Lett), in the article, "Detection of oxygen and carbon in the upper atmosphere of the extra-solar planet HD 209458b."

Adapted from the press release at http://uanews.org/cgi-bin/WebObjects/UANews.woa/5/wa/SRStoryDetails?ArticleID=8571.

(Added 02/07/04) Galaxy formation is still a hot topic of debate among astronomers - there are various theories that have been proposed, but there is still none that is irrefutable. Astronomers using the National Science Foundation's Green Bank Telescope (GBT) has now made the first conclusive detection of what look like leftover building blocks of galaxy formation - neutral hydrogen clouds - surrounding the Andromeda Galaxy, also known as M31, which is the largest spiral galaxy to the Milky Way.

The discovery may help scientists understand the structure and evolution of the Milky Way and other spiral galaxies. It may also help to explain why some young stars in older galaxies do not have a lot of heavy elements that most others contain. "Giant galaxies, like Andromeda and our own Milky Way, are thought to form through repeated mergers with smaller galaxies and through the accretion of vast numbers of even lower mass 'clouds' - dark objects that lack stars and even are too small to call galaxies," explained David A. Thilker of the Johns Hopkins University in Baltimore, Maryland. "Theoretical studies predict that this process of galactic growth continues today, but astronomers have been unable to detect the expected low mass 'building blocks' falling into nearby galaxies, until now."

Previous studies have revealed a number of clouds of neutral atomic hydrogen that are near the Milky Way but not part of its disk. These were initially referred to as high-velocity clouds (HVCs) when they were first discovered because they appeared to move at velocities difficult to reconcile with the Milky Way's rotation. Scientists were uncertain if HVCs comprised building blocks of the Milky Way that had so far escaped capture, or if they traced gas accelerated to unexpected velocities by energetic processes (multiple supernovae) within the Milky Way. The discovery of similar clouds bound to the Andromeda Galaxy strengthens the case that at least some of these HVCs are indeed galactic building blocks.

Astronomers are able to use radio telescopes to detect the characteristic 21-cm radiation emitted naturally by neutral atomic hydrogen. The great difficulty in analyzing these low-mass galactic building blocks has been that their natural radio emission is extremely faint. Even those nearest to us, clouds orbiting our galaxy, are hard to study because of large distance uncertainties. "We know the Milky Way HVCs are relatively nearby, but precisely how close is maddeningly tough to determine," said Thilker. Past attempts to find missing satellites around external galaxies at well-known distances have been unsuccessful because of the need for a very sensitive instrument capable of producing high-fidelity images, even in the vicinity of a bright source such as the Andromeda Galaxy.

One might consider this task similar to visually distinguishing a candle placed adjacent to a spotlight. The novel design of the recently commissioned GBT met these challenges brilliantly, and gave astronomers their first look at the cluttered neighborhood around Andromeda. The Andromeda Galaxy was targeted because it is the nearest massive spiral galaxy. "In some sense, the rich get richer, even in space," said Thilker. "All else being equal, one would expect to find more primordial clouds in the vicinity of a large spiral galaxy than near a small dwarf galaxy, for instance. This makes Andromeda a good place to look, especially considering its relative proximity - a mere 2.5 million light-years from Earth."

What the GBT was able to pin down was a population of 20 discrete neutral hydrogen clouds, together with an extended filamentary component, which, the astronomers believe, are both associated with Andromeda. These objects, seemingly under the gravitational influence of Andromeda's halo, are thought to be the gaseous clouds of the "missing" (perhaps dark-matter dominated) satellites and their merger remnants. They were found within 163,000 light-years of Andromeda.

Favored cosmological models have predicted the existence of these satellites, and their discovery could account for some of the missing "cold dark matter" in the Universe. Also, confirmation that these low-mass objects are ubiquitous around larger galaxies could help solve the mystery of why certain young stars, known as G-dwarf stars, are chemically similar to ones that evolved billions of years ago. As galaxies age, they develop greater concentrations of heavy elements formed by the nuclear reactions in the cores of stars and in the cataclysmic explosions of supernovae. These explosions spew heavy elements out into the galaxy, which then become planets and get taken up in the next generation of stars.

Spectral and photometric analysis of young stars in the Milky Way and other galaxies, however, show that there are a certain number of young stars that are surprisingly lacking of heavy elements, making them resemble stars that should have formed in the early stages of galactic evolution. "One way to account for this strange anomaly is to have a fresh source of raw galactic material from which to form new stars," stated Edward Murphy of the University of Virginia. "Since high-velocity clouds may be the leftover building blocks of galaxy formation, they contain nearly pristine concentrations of hydrogen, mostly free from the heavy metals that seed older galaxies." Their merger into large galaxies, therefore, could explain how fresh material is available for the formation of G-dwarf stars.

Adapted from the press release at http://www.nrao.edu/pr/2004/m31HVCs/.

(Added 01/31/04) With Spirit recovering and Opportunity rolling onto the Martian surface, it appears as if the rovers can get back to doing science. Mars Exploration Rover (MER) Opportunity's First Steps

The Opportunity rover, the second to have arrived on Mars of the pair, rolled off its ramp onto the soil this Saturday morning. Conformation of the successful drive off the lander came at 3:01 A.M. PST via the Mars Odyssey orbiter. The rover, approximately 1 meter (3 ft) from the lander, sent back the image to the right; the image was taken with the rover's rear hazard camera. It was Opportunity's seventh day ("sol") on Mars.

A mineral called "hematite" that is formed on Earth by water at the bottom of lake beds has been found in the soil of the crater in which Opportunity currently resides. Dr. Phil Christensen, lead scientist for both the rovers' miniature thermal emission spectrometers, announced that "as we get out of the bowl we're in, I think we'll get onto a surface that is rich in hematite." The mineral was found using the craft's spectrometer.

Meanwhile, on the opposite side of the planet, the rover Spirit has resumed taking pictures as engineers continue to restore its good health. Spirit transmitted a picture on Thursday that shows its arm is exactly where it is supposed to be, with its Moessbauer spectrometer positioned against the rock "Adirondack." Several other tests were conducted on Thursday.

The first science data in over a week was sent to Earth from Spirit on Friday, January 30. Microscopic images and spectroscopic data of Adirondack taken on January 22 has been returned, and they show that Adirondack is a hard, crystalline rock. "If you had a hammer and whacked that rock, it would ring," explained Dr. Ray Arvidson of Washington University in St. Louis, deputy principal investigator for the rover science instruments.

The spectrum of the rock allows scientists to determine what types of iron-bearing minerals are contained within it. The peaks of the spectrum show that Adirondack includes olivine, pyroxene, and magnetite - a composition common to volcanic basalt rocks on Earth. In the coming days, scientists plan to use Spirit's rock abrasion tool to grind the surface in a small volume away, in order to inspect its interior. Later plans include examining a nearby whitish rock and then driving to a crater named "Bonneville" that's about 250 m (820 ft) away.

Adapted from the press releases http://www.jpl.nasa.gov/releases/2004/47.cfm, http://www.jpl.nasa.gov/releases/2004/44.cfm, and http://www.jpl.nasa.gov/releases/2004/46.cfm.

(Added 01/29/04) The Hubble Space Telescope (HST) revolutionized astronomy and has continued to do so for over a decade. It was slated to be retired in 2010, a year before its successor, the James Webb Space Telescope, was to come online in 2011. On January 16, NASA Administrator Sean O'Keefe announced that the HST will be retired three years early.

The ability for Hubble to continue to make an impression on astronomy comes not only from its vantage point above the blurring effects of Earth's atmosphere, but it had been routinely upgraded with new instruments, gyros used for stabilization, and batteries. A 2006 servicing mission (SM4) to the telescope would have extended its life to some time in 2010.

But because of the redistribution of NASA's budget, mostly due to the Bush plan (see story below), and the recommendations of the Columbia Accident Investigation Board, the final shuttle servicing mission has been canceled. The Accident Investigation Board recommended that for any shuttle mission, NASA must be able to examine the shuttle from orbit. This is relatively easy at the altitude of the International Space Station (ISS), but HST is higher up and so it would be harder to fulfill this requirement. The added cost of this was the most likely cause of O'Keefe's announcement.

Hubble is now at the mercy of its aging equipment. It is working on three good gyros with one that is a backup in case the others fail. It needs three to correctly point and track objects, but engineers are working on software that should allow it to work well on just two gyros. The batteries are what will probably fail first, and they will most likely do so in 2007.

Even if the gyros and batteries continue to function, there is still the problem of the Hubble's decaying orbit. Atmospheric drag on the telescope perpetually lowers its orbit. Every servicing mission, shuttle astronauts raised it back to a higher orbit to help prolong its life, but eventually it will enter the atmosphere. Current suggestions are for a small robotic craft to latch onto Hubble and direct its decent so that it will not impact an inhabited area.

Proposals for observing time during what could be Hubble's last year were due last Friday, January 23 at 5:00 P.M. EDT. The American Astronomical Society (AAS) has yet to announce its official position on the matter, but the AAS Council has adopted a resolution that calls for an independent outside panel to review the situation.

Adapted from the journal article: Reichhardt, Tony. "NASA's Drive to Revisit the Moon Leaves No Scope for Hubble." Nature, 427, p. 273 (2004).

(Added 01/26/04) Early Wednesday, January 21, 2004, ground controllers encountered problems with communication with the Mars Exploration Rover Spirit. They were able to send commands to the craft, and received a simple signal acknowledging that the rover heard them, but they did not receive the expected scientific and engineering data during scheduled communications sessions that day.

Thursday morning, Sprit sent a simple radio signal acknowledging that the rover had received a transmission from Earth. The situation was classified as "critical." No single explanation considered fits the events that occurred, but by Friday, Spirit sent a signal that lasted for 10 minutes and sent data at a rate of 10 bits per second. Subsequent communications sessions lasted 20 minutes and 15 minutes.

Mars Exploration Rover (MER) Spirit Landing Site from Mars Global Surveyor The current theory of the malfunction is that the flight software is not functioning normally. It appears as if it rebooted the rover's computer more than 60 times from Wednesday through Friday. A motor that moves a mirror for the rovers's infrared spectrometer was partway through an operation when the problem arose, so the possibility of a mechanical problem with that hardware is a theory as to the cause.

On Friday, January 23, it did not go to sleep even after ground controllers told it to twice. Ground controllers were surprised on Friday when Spirit, via Mars Odyssey, sent 73 megabits of data at a rate of 128 kilobits per sec; it included power subsystems engineering data, no science data, and several frames of "fill data" - sets of random numbers.

On Saturday, January 24, its status was upgraded to "serious" when engineers were able to communicate reliably with the craft and get it to stop rebooting many times per day. Responses to commands sent Saturday morning confirmed the theory that the problem is related to the rover's two "flash" memories or software controlling those memories. This was confirmed when commands were sent to use the random-access memory instead of flash memory and the subsequent commands were successfully interpreted.

Mars Exploration Rover (MER) Spirit - Rock Adirondack By commanding Spirit each morning into a mode that avoids the flash memory, engineers plan to get it to communicate at a higher data rate, diagnose the root cause of the problem, and develop ways to restore as much functionality as possible.

Prior to the communication problems, Spirit was set out to examine the rock named "Adirondack," which is shown in the picture to the left. It was chosen as the first target because is is dust-free and has a flat surface that is ideally suited for grinding. Clean surfaces are also better for examining a rock's top coating.

On January 19, the Mars Global Surveyor took a high-resolution optical image of Spirit's landing site. Visible (and marked in the image above on the right) are discolorations due to the airbags when the craft bounced during landing. Also visible is the heat shield's landing position and the parachute's.

Adapted from the NASA press releases 2004-027, 2004-28, 2004-29, 2004-30, 2004-31, 2004-33, 2004-34, and http://www.jpl.nasa.gov/mer2004/rover-images/jan-19-2004/captions/image-2.html.

(Added 01/26/04) Aboard the NASA suborbital Black Brant rocket that launched last week was a telescope/spectrometer combination that searched the UV spectrum of Mercury and for the long-sought after but yet unfound belt of asteroids called "Vulcanoids" that have been theorized to lie between the sun and Mercury.

The main spectrograph is designed to observe objects too close to the sun for the Hubble Space Telescope (HST) and other orbital instruments to view. With the data gathered, new details about Mercury's surface composition should be revealed. It is also hoped that there will be observations of Vulcanoids.

Vulcanoids are a hypothesized population of small asteroids that is exceedingly difficult to observe from the ground because of its proximity to the sun. Researchers have made several ground-based searches during early morning and late evening twilight as well as during solar eclipses, but none have been found.

Adapted from the press release on http://www.swri.edu/9what/releases/suborb.htm.

(Added 01/26/04) The Pleiades, a collection of stars that form an open cluster, has been used for millennia in myths, legends, and navigation. Now, a group of astronomers has obtained a highly accurate distance to the star Atlas in the cluster. The new results will be useful in improving the cosmic distance ladder as well as understanding star life cycles.

The team of astronomers, reporting in the January 22 issue of Nature, are from the California Institute of Technology and NASA's Jet Propulsion Laboratory. They have determined that the star is 434-446 light-years from Earth - highly accurate by astronomical standards.

The measurement settles a controversy that had arisen when the European satellite Hipparcos measured a much shorter distance to the Pleiades than expected and contradicted theoretical models of the life cycles of stars. The Hipparcos measurements suggested that either the measurements were off or something was wrong with models of stellar life cycles. The new results show that the former was the issue.

The new distance measurement is based upon interferometry. Observations of the star and its binary companion allowed the orbital period of the two stars to be measured. Knowing the time it takes the two stars to orbit each other and combining it with basic physics allowed the team to determine the distance between the two stars, and with this to then calculate their distance to Earth.

Adapted from the press release on http://www.jpl.nasa.gov/releases/2004/26.cfm.

(Added 01/26/04) NASA's done it again with their Mars Exploration Rover (MER) Program. The second craft, Opportunity, successfully landed January 25, 2004 at about 05:05 GMT, in a small impact crater on Mars. the region, Meridiani Planum, was selected because of extensive deposits of the mineral crystalline hematite, which usually forms in the presence of liquid water.

Mars Exploration Rover (MER) Opportunity's Vista Images have already been returned to Earth, and show a large crater which could provide access to deeper layers of the soil that lies nearby the craft. The crater is about 150 m (500 ft) across and within 1 km (0.5 mile) of the landing site says Dr. Andrew Johnson of JPL, an engineer for the descent imaging system.

Before Opportunity heads into the wild unknown, it will spend one to two weeks getting ready. Its status is "excellent," and has successfully communicated with Earth through the Mars Odyssey craft. Direct communications between Opportunity and Earth were attempted on the evening of January 25.

Several images have already been returned by Opportunity. One of the first images was a 360° panorama of the surrounding area, as had its twin, Spirit, produced on its first day. Another is of the landscape near the lander, and is shown to the left. If one compares it with the image taken of the surroundings of Spirit, it is clear that the terrain is very different. The land is of a type that has never been seen on Mars. Also visible in the image are circular areas that were created by Opportunity's air bags.

Adapted from the press release on http://www.jpl.nasa.gov/releases/2004/37.cfm.

(Added 01/26/04) The ESA's Mars Express, which successfully entered into Mars orbit on December 25, 2003, has begun to collect images and spectra of the Martian surface.

Mars Express 3-D Rendering of Valles Marineris The first stereo color image was taken on January 14, 2004 from an altitude of 275 km (171 miles) by its High Resolution Stereo Camera. The picture, is of a section of Valles Marineris, and is the first image of its size that shows the surface of Mars in high resolution (12 m per px), color, and 3-D. With the stereoscopic data, scientists can render the landscape to show how it would appear from any altitude or angle. The left image shows such a rendering, as one would see the landscape in a low-flying aircraft.

Besides beautiful images, Mars Express has discovered water on Mars. During an initial mapping of the south polar cap on January 18, the OMEGA instrument found water ice and carbon dioxide ice (AKA dry ice). The find was confirmed by the PFS instrument, a high-resolution spectrometer.

Adapted from the press releases on http://www.esa.int/export/esaCP/SEMWF0474OD_index_0.html and http://www.esa.int/export/esaCP/Pr_6_2004_p_EN.html.

(Added 01/16/04) Flight controllers have learned of the Mars Exploration Rover (MER) Spirit's precarious landing on Mars nearly two weeks ago, and it's probably a good thing that they couldn't watch.

Spirit's parachute deployed when the craft was only 4.6 miles - a mile lower than it should've - above the surface, and its braking rockets fired only 34 stories above the surface. The parachute deployed late because of a dust storm on the other side of the planet, causing the density of the atmosphere above Spirit's landing site to be different than expected.

The parachute caused the craft to decelerate from 920 mph to 152 mph - slower than expected. The severity of the slowdown could be attributed to updrafts of the higher atmospheric density. But even this speed is 30% faster than a free-falling skydiver.

As the craft drew closer to the surface, a sudden gust of wind pushed the lander toward a 650-foot-wide crater, but the on-board computer compensated and fired rockets to counteract the motion. Then, the airbag-encased lander was cut free from its parachute when it was just 28 ft above the surface - more than 10 ft lower than expected.

Finally, the lander hit the ground and bounced 28 times across nearly 1000 ft before rolling to a stop 57 seconds later. Spirit came to a rest 820 ft from the crater, which will be its first target of surface exploration (see story below).

Adapted from an article on Spaceflight Now's website at http://spaceflightnow.com/mars/mera/040113reconstruction.html.

"... Much remains for us to explore and to learn. In the past 30 years, no human being has set foot on another world, or ventured farther upward into space than 386 miles - roughly the distance from Washington, D.C. to Boston, Massachusetts. America has not developed a new vehicle to advance human exploration in space in nearly a quarter century. It is time for America to take the next steps."

(Added 01/16/04) With these words, U.S. President George W. Bush prompted NASA to take a new direction, aimed at further solar system exploration with humans. President Bush outlined several goals:

"Our first goal is to complete the International Space Station by 2010. To meet this goal, we will return the Space Shuttle to flight as soon as possible. ... In 2010, the Space Shuttle - after nearly 30 years of duty - will be retired from service. Our second goal is to develop and test a new spacecraft, the Crew Exploration Vehicle, by 2008, and to conduct the first manned mission no later than 2014. ... The main purpose of this spacecraft will be to carry astronauts beyond our orbit to other worlds. This will be the first spacecraft of its kind since the Apollo Command Module.

"Our third goal is to return to the moon by 2020, as the launching point for missions beyond. Beginning no later than 2008, we will send a series of robotic missions to the lunar surface to research and prepare for future human exploration. ... With the experience and knowledge gained on the moon, we will then be ready to take the next steps of space exploration: Human missions to Mars and to worlds beyond."

In spite of the majestic words by our Nation's 43^th president, there are mixed reactions to his goals. Many blame the initiative on China's manned spaceflight last October, seeing this as a new space race, as had been conducted between the U.S. and former U.S.S.R. over four decades ago.

The funding for such endeavors - a manned mission to Mars has been estimated to cost an excess of $1 trillion - has not been specified. President Bush plans on increasing NASA's budget by $1 billion over the next five years, while another $11 billion will be reallocated from NASA's $86 billion budget over five years. The President's father also instigated a similar push during his presidency over a decade ago, but it never got off the ground (so to speak) due to budget problems.

The eloquent speech is a good launch platform for extended exploration, however, only time will tell if the initiative will come to fruition.

Adapted from the press releases on http://www.whitehouse.gov/news/releases/2004/01/20040114-3.html and http://www.whitehouse.gov/news/releases/2004/01/20040114-1.html, the quotes coming from the former.

(Added 01/16/04) A team of astronomers led by the University of Florida (UF) may have discovered the biggest and brightest star ever found - the star is as much as seven times brighter than the current record holder, the Pistol Star.

5,000,000 times brighter than the sun, the star, named LBV 1806-20, is not visible to the naked eye because dust between us and the star, 45,000 light-years away, absorbs all of the visible light from the star. Hence, it is only visible to infrared light - light of longer wavelengths that can better penetrate the dust.

The problem with identifying such a bright star is that it is hard to tell the difference between it and a close cluster of stars. However, in the case of this star, "the high-resolution data prove that the object is not simply a cluster of lower mass stars, although it is possible that it is a collection of a few stars in a tight orbit around each other. More study will be needed to determine the distance and singularity of the object in order to establish whether the object is truly the most massive star known," explained Don Figer, an astronomer at the Space Telescope Science Institute who led the team that discovered the Pistol Star in 1997.

If a single star, it is an extremely luminous blue variable star, and it is at least 150 times larger than the sun. LBV 1806-20 is estimated at less than 2 million years old; this is in stark contrast with our solar system, estimated at being about 5 billion years old.

A mystery is how the star got so big. Current theories of star formation suggest that they should be limited to about 120 times the mass of the sun. This is because the heat and pressure from such big stars' cores would force matter away from the surfaces, effectively destroying anything larger. A possible explanation would be a shock-induced formation, which occurs when a supernova blows up and slams the material in a nebula into a massive star.

The star is not the only unusual specimen in its neighborhood, for it is located in a small cluster of highly unusual or extremely rare stars. One of these is a soft gamma ray repeater, which is a neutron star with a magnetic field hundreds of trillions of times more powerful than Earth's. Only four stars are known to be soft gamma ray repeaters. Another unusual star in the cluster is one that is extremely young.

Adapted from the press release on http://www-int.stsci.edu/~figer/web/LBV1806-20/bigbrightstar.htm.

(Added 01/16/04) Astronomers from the University of Arizona (UA) have detected a lensed quasar more than twice as wide as any previously reported. The study of such quasars can help us to learn more about dark matter and how it was distributed in the early universe.

"When you've got pockets of the most dark matter,that's where clusters of galaxies form," explained Andrew Marble, a doctoral candidate in astronomy at UA. "Wide lenses probe what the universe looked like back in time and are a way of detecting dark matter."

The quasar, QSO 2QZ J1435+0008, was imaged by Marble and his colleagues in March of 2003 using the 6.5-meter UA/Smithsonian MMT on Mount Hopkins, AZ to look at what appeared to be quasar pairs. "We didn't go to the telescope expecting to find a gravitational lens because nobody had ever seen such a wide one before." But, when the data were analyzed, the images of the two quasars were at the same distance from Earth, and other aspects of the quasars' spectra were nearly identical.

Thus, Marble and his colleges believe they've "discovered the widest-separation lens yet. Ours is bigger than others." The distance between the two images is 33 arcsec; the next-biggest gravitational lens known is only about half that size, and the average lens is 20 times smaller.

Adapted from the press release on http://uanews.org/cgi-bin/WebObjects/UANews.woa/3/wa/SRStoryDetails?ArticleID=8404.

(Added 01/16/04) NASA scientists have been busy the last few days, doing what many college students around the country dream about: planning a road trip. Only this trip involves no roads and will be exploring an area hundreds of millions of miles from home. Again, a college student's dream, but now take into consideration that this trip will explore a world without breathable atmosphere and where no human has ever been: Mars.

The first step was to get an accurate map of the area, and to try to pinpoint where the craft landed. Orbital images combined with ground-based images have allowed for a relatively accurate location. The rover successfully rotated on the lander platform on Tuesday, January 13, and rolled off the lander on Thursday, January 15. It is now set for its exploration.

MER Spirit Looking Back at Lander The first point of interest is a crater that is about 250 m (270 yd) northeast of the lander. "We'll be careful as we approach. No one has ever driven up to a Martian crater before," Dr. Steve Squyres of Cornell University, Ithaca, NY, Principal Investigator for the science payload. The crater is about 200 m (220 yd) wide, and the impact that caused it probably flung rocks several meters away from it, where Spirit can examine them.

After the rover is finished with the crater, it will head towards the mountains seen in Eastward photographs (right image). The hills are about 3 km (2 miles) away, which is about five times as far as NASA's mission-success criteria for how far the rover should drive. The highest hill rises about 100 m (110 yd) above the plain.

As any proud parent will attest, the first steps to an infant's independence is its first steps. And so, much rejoicing was had as the Spirit rover took its "first steps" onto the Martian soil yesterday, successfully driving off the lander at 08:41 UT. "Spirit is now ready to start its mission of exploration and discovery. We have six wheels in the dirt," proclaimed JPL Director, Dr. Charles Elachi. The left image shows the hazard camera looking back at the lander, which had been the rover's home for the last 12 Sol - Martian days.

Adapted from the press releases on http://www.jpl.nasa.gov/releases/2004/19.cfm, http://www.jpl.nasa.gov/releases/2004/18.cfm, and http://www.jpl.nasa.gov/releases/2004/20.cfm.

(Added 01/16/04) The bright red star in the constellation Orion's shoulder has been imaged by the Hubble Space Telescope (HST), and its observations directly show hot gas escaping its atmosphere at a larger distance than from any other star. The team of astronomers has been studying Betelgeuse's atmosphere for the past five years with HST, and they found that the bubbling action of the chromosphere tosses gas out one side of the star while it falls into the star on the other side.

The star's chromosphere - the inner atmosphere, between the photosphere and corona - extends more than 50 times its radius in visible light; if it were in the solar system, this would be five times beyond Neptune's orbit. "Betelgeuse's upper chromosphere extends into the enormous cloud of cold dust around this supergiant star. Our basic knowledge of how chromospheres form should explain how it sends this warm gas so far into space. There is plenty of gas below 2000 °F because of dust, but this gas is apparently joined by much hotter ionized gas from the chromosphere near the star's surface" said Alex Lobel, leader of the team.

A match flame warms air above it, causing the heat to quickly dissipate into the cooler air around the flame. In Betelgeuse's upper atmosphere, hot and cold gas mix together, but the warm gas does not entirely dissipate until far above the colder gas. The new HST data show that remote parts of the chromosphere contain gas above 2600 K (4220 °F), but the cold neighboring gas is below 1500 K (2240 °F).

Adapted from the press release on http://cfa-www.harvard.edu/press/pr0403.html.

(Added 01/07/04) Calling home from the Gusev Crater, Mars, NASA's Mars Exploration Rover (MER) craft "Spirit" succeeded in contacting Earth at 11:35 P.M. EST, in what NASA Administrator Sean O'Keefe says is "a big night for NASA. We're back ... and we're on Mars."

It took a journey of about seven months and 487 million km (303 million miles) to reach Mars, and after landing on January 3, 2004, it has already shattered previous Mars records with clarity and resolution in its images.

Gustov Crater Plains, Imaged by Mars Exploration Rover (MER) Spirit The team was looking for an area that was flat and had exposed rocks - a terrain different from the Viking and Pathfinder sites. "What we're seeing is a section of surface that is remarkably devoid of big boulders, at least in our immediate vicinity, and that's good news because big boulders are something we would have trouble driving over. We see a rock population that is different from anything we've seen elsewhere on Mars, and it comes out very much in our favor," explains Dr. Steve Squyres of Cornell University, Ithaca, NY, Principal Investigator for the science payload.

The image above and to the right is of the lander, taken by the camera on the long pole at the 7:30 position. The image to the left shows the plains around the area. This is a drastically scaled-down version, for the full resolution was over 50x50 inches.

Several wide, shallow bowls are near the lander, and they may be impact craters. Mission scientists plan on sending the tiny rover to one that has been named "Sleepy Hollow." It is about 9 m (30 ft) across and 12 m (40 ft) north of the lander.

Adapted from the press releases on http://www.nasa.gov/home/hqnews/2004/jan/HQ_04002_spirit_wrap.html, http://www.nasa.gov/home/hqnews/2004/jan/HQ_04005_spirit_update_04jan.html, and http://www.nasa.gov/home/hqnews/2004/jan/HQ_04008_spirit_update_0105.html.

(Added 01/07/04) NASA's Stardust spacecraft has completed its primary mission, as of January 2, 2004 - to journey near enough to comet P/Wild 2 to deploy a tennis racket-like collector to retrieve pristine samples of the comet.

Stardust's closest approach to the comet, pronounced "Vilt-2," occurred at 19:22 UT at a distance of only 230 km (143 miles). It contacted Earth 21 min 40 sec later, informing mission control that it had succeeded in the most difficult part of its mission. "Things couldn't have worked better in a fairy tale," said Tom Duxbury, Stardust program manager at NASA's Jet Propulsion Laboratory in Pasadena, CA.

Stardust has traveled about 3.22 billion kilometers (2 billion miles) since its launch on February 7, 1999. As it approached its target, the craft endured endured a bombardment of particles surrounding the nucleus of comet Wild 2. To protect Stardust against the blast of expected cometary particles and rocks, the spacecraft rotated so it was flying in the shadow of its "Whipple Shields." The shields are named for American astronomer Dr. Fred L. Whipple, who, in the 1950s, came up with the idea of shielding spacecraft from high-speed collisions with the bits and pieces ejected from comets. The system includes two bumpers at the front of the spacecraft -- which protect Stardust's solar panels -- and another shield protecting the main spacecraft body. Each shield is built around composite panels designed to disperse particles as they impact, augmented by blankets of a ceramic cloth called Nextel that further dissipate and spread particle debris.

Stardust has now taken the "best pictures ever ... of a comet," explains the Principal Investigator Dr. Don Brownlee of the University of Washington, Seattle. The image on the right is that of Wild 2's nucleus - the only solid and permanent part of a comet. "Although Stardust was designed to be a comet sample return mission, the fantastic details shown in these images greatly exceed our expectations." The data took approximately 30 hours to return to Earth.

Mission scientists now have the images collected, but they will need to wait another two years, until January 15, 2006, before the collected particles, stowed in a sample return capsule onboard Stardust, will be returned to Earth for in-depth analysis. The capsule makes a soft landing at the U.S. Air Force Utah Test and Training Range. The microscopic particle samples of comet and interstellar dust collected by Stardust will be taken to the planetary material curatorial facility at NASA's Johnson Space Center, Houston, TX, for analysis.

Adapted from the press release on http://www.jpl.nasa.gov/releases/2004/7.cfm and the JPL release "NASA Spacecraft Makes Great Catch ... Heads for Touchdown" on 01/02/04.