Hubble Heritage Archive

Hubble Heritage Archive - 1999

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Gemini | Apollo | Hubble Space Telescope

M57 - Ring Nebula - NGC 6720 January's Hubble Heritage image is of NGC 6720, AKA M57, AKA the Ring Nebula, a planetary nebula. 2,300 light-years from us, the Ring Nebula lies in the constellation Lyra; this image covers approximately 2 arcminutes down (1.3 light-years). The image was originally taken on February 7, 1999, and October 16, 1998, for a total exposure time of 1 hour.

M57 is the most famous of all planetary nebulae. This Hubble image is the sharpest ever taken of it. In the image, the orbiting telescope is looking through a tunnel of gas that has been cast off by a dying star thousands of years ago.

In the image can be seen elongated dark clumps of material embedded in the gas at the edge of the nebula. The central dying central star is floating in the middle of the blue, hot gas.

The nebula itself is about 1 light-year in diameter. The colors are approximately true colors. Blue represents helium, green is oxygen, and red is nitrogen.

February's Hubble Heritage image is of SN1987A, a supernova remnant in the Large Magellanic Cloud. 168,000 light-years from us, SN1987A lies in the constellation Dorado; this image covers approximately 2.6 arcminutes down (130 light-years). The image was originally taken in September 1994, February 1996, and July 1997, for a total exposure time of 8.3 hours.

The star that created this remnant, seen in the very center of the image surrounded by two sets of rings, went supernova on February 23, 1987. Several of the bright blue nearby stars are very massive, each weighing about six times that of the sun. Their ages are around 12 million years, and they are members of the same generation as the star that went supernova.

The bright clouds show another sign of the youth of this region. In a few years, the supernova's material will sweep the inner ring, heating and exciting its gas, and it will produce a series of "cosmic fireworks" that will be visible for over a decade.

LL Orionis March's Hubble Heritage image is of an asteroid trail in the constellation Centaurus. This image covers approximately 2.7 arcminutes down. The image was originally taken on April 6, 1994, for a total exposure time of 33 minutes.

The Hubble Space Telescope was performing a detailed study of Proxima Centauri using the Fine Guidance Sensors to search for small deviations that could indicate an unseen planetary companion.

In a program initiated by Dr. Ed Groth of Princeton, the Wide Field and Planetary Camera 2 was activated to make use of otherwise wasted time. It was looking at a typical Milky Way star field in Centaurus, and such images can be used to study the evolution of stars that make up our galaxy. Most of the stars seen lie about 25,000 light-years away.

However, the blue streak in the upper right is an un-catalogued, mile-wide asteroid only light-minutes away that happened to stray into the field of view. This asteroid is much to faint to be seen and tracked from the ground, so precise orbital calculations could not be made. It could cross Mars' path. About 100 such asteroids have been found in this manner.

April's Hubble Heritage image is of Hodge 301, a nebulous region in our galaxy. 168,000 light-years from us, Hodge 301 lies in the constellation Dorado; this image covers approximately 118 arcseconds down (96 light-years). The image was originally taken on December 17, 1995, for a total exposure time of 1.8 hours.

Hodge 301 is a highly active starburst region with a cluster of luminous, massive stars. It appears in the lower right corner of this image, and lies in the Large Magellanic Cloud.

Many of the stars in this cluster are so old that they have exploded as supernovae. The blasts of material from these have plowed through the surrounding Tarantula Nebula, shocking and compressing the gas into many sheets and filaments, seen in the upper left of this image. These features move away from the cluster at speeds in excess of 322 km per sec (200 miles per sec).

There are three red supergiants in the cluster, slated to go supernova in the next few million years. Also, near the center of the image are small, dense globules of gas and dust where new stars are being formed.

NGC 4650A - Polar Ring Galaxy May's Hubble Heritage image is of NGC 4650A, a polar-ring galaxy. 130 million light-years from us, NGC 4650A lies in the constellation Centaurus; The ring is approximately 60,000 light-years in diameter. The image was originally taken on April 7-9, 1999, for a total exposure time of 5.6 hours.

This image is courtesy of an 8,000 person internet poll of what Hubble should view. NGC 4650A is only one of 100 known polar-ring galaxies. The unusual disk-ring structure is not yet understood fully.

One possibility is that polar rings are the remnants of huge collisions between two galaxies in the past, probably over 1 billion years ago. What is left of one galaxy is now the rotating inner disk of old red stars in the center. The second, smaller galaxy was destroyed, but gas from it was stripped and captured, forming a new ring of dust, gas, and stars, which now orbit the inner galaxy at an almost right angle to the old larger galaxy.

This image displays features that were previously unknown. It confirms that the bright, central concentration of light (orange in this image) has a completely smooth and regular appearance, indicating that it is a dense system composed of older stars with little interstellar gas or dust.

The central dark lanes are from clouds of dust and gas that block the optical light of stars behind them. These clumps, though, are also sites of star formation, shown by the bluish clumps that are especially prominent in the outer parts of the ring.

The polar ring itself is highly distorted with no regular pattern. Because it extends far into the halo of NGC 4560A, it provides a good opportunity to map the dark matter which is thought to surround most disk galaxies. The alignment of the ring along the pole of the inner disk's rotation allows scientists to study the gravity and thus the distribution of dark matter.

June's Hubble Heritage image is of NGC 4414, a spiral galaxy. 63 million light-years from us, the NGC 4414 lies in the constellation Coma Berenices; this image is about 2.4 arcminutes down, and the galaxy is about 56,000 light-years in diameter. The image was originally taken in April/June 1995 and April 1999, for a total exposure time of 3.5 hours.

This galaxy was originally imaged in 1995 as part of a project to learn more about the extragalactic distance scale. An international team of astronomers contributed to this. Based on the discovery and measurement of variable stars in NGC 4414, they were able to make accurate distance measurements to the galaxy. This, and other galaxies, have helped cosmologists learn about the Hubble Constant - the rate of expansion of the universe.

Only half of the galaxy was visible due to its large size. Thus, in 1999, Hubble Heritage Team imaged the other half in the same way as was done four years prior. The new picture shows the dusty spiral galaxy with an older, yellow central region and outer arms that are bluer with young stars, the brightest of which can be seen individually in this image.

NGC 6093 - M80 - Globular Cluster July's Hubble Heritage image is of M80, AKA NGC 6093, a globular cluster. 28,000 light-years from us, M80 lies in the constellation Scorpius; the image is about 3 arcminutes down. The image was originally taken in October 1994, January and April 1996, and August-October, 1997.

This globular cluster is one of the densest known in the Milky Way; it contains hundreds of thousands of stars. All born at approximately the same time but possessing a range of masses, globular clusters such as this present a convenient way for learning about stellar evolution.

Particular in this cluster is a large population of "blue stragglers" at the core of the cluster. These stars are unusually young and massive in comparison with the other stars in the globular cluster. It is thought that these may have arisen from stellar mergers. M80 was previously not known to possess any blue stragglers, but it is now believed that it might contain up to twice as many as in any other globular cluster.

Another unusual feature of M80 is that it is the site of a nova explosion in 1860. This type of explosion occurs when a close companion in a binary system transfers hydrogen to a white dwarf star. Eventually, the hydrogen ignites on the surface of the star. The remnant, T Scorpii, was found in the 19^th century, but other observations have found only two other such explosions, which is far fewer than models show should exist.

August's Hubble Heritage image is of Jupiter's Great Red Spot, a high-pressure cyclonic storm. Jupiter lies an average of 5.2 A.U. from from the sun. The images were taken in May 1992, July and August 1994, February and October 1995, October 1996, April 1997, and June 1999.

The Great Red Spot (GRS) has been visible on Jupiter ever since telescopes were first turned towards the king of the solar system - over 300 years. It is a vast, cyclonic storm, rotating in a counterclockwise direction in Jupiter's southern hemisphere at speeds of about 435 km per hour (270 mph). It is the largest known storm in the solar system, possessing a diameter of about 24,800 km (15,400 miles), being about twice the size of Earth and 1/6 the diameter of Jupiter.

The GRS does vary in size, shape, and color, but it will probably remain on Jupiter for centuries to come. It is constantly fueled by the rotation energy of the planet as well as smaller storms that it devours. Jupiter also lacks a solid surface that could dissipate the storm energy, which is what happens when hurricanes hit land on Earth.

One of the reasons the GRS is studied is that understanding weather phenomena on other planets can be applied to understanding and predicting weather on Earth. GRS studies are applicable to studying large storms that occur over oceans on Earth, which is the closest approximation to Jupiter's anatomy as Earth has.

September's Hubble Heritage image is of Hickson Compact Group 87 (HCG 87), an interacting cluster of galaxies. 400 million light-years from us, HCG 87 lies in the constellation Capricorn; the galaxy group has a diameter of approximately 170,000 light-years. The image was originally taken on July 19-25, 1999, for a total exposure time of 6.6 hours.

This group of four galaxies is interacting from the mutual gravitational forces between them. The interaction will occur over a time span of hundreds of millions of years.

The high resolution of Hubble is needed to reveal many of the intricacies of this cluster. In particular, it shows complex details of the dust lanes in the group's largest member, HCG 87a, a disk-shaped galaxy that is at an angle so that we see it nearly edge-on.

Both 87a and the neighboring elliptical, 87b, are active galaxies, meaning that it is believed that their nuclei possessblack holes that are currently consuming gas. The nearby spiral, 87c, may be undergoing a burst of active star formation. This is probably due to the gravitational tidal forces between the interacting galaxies that cause gas to flow between them.

Spectral analysis of the small spiral galaxy near the center of the group is inconclusive in that it could be either a fourth member of the group or an unrelated background object.

The image has been color coded so that regions of active star formation are blue and also pinkish if there is hot hydrogen gas.

Hubble's Variable Nebula - NGC 2261 - R Monocerotis Nebula October's first Hubble Heritage image is of NGC 2261, AKA R Monocerotis Nebula, AKA Hubble's Variable Nebula, a reflection nebula. 2,600 light-years from us, the Hubble's Variable Nebula lies in the constellation Monoceros; this image covers approximately 2.5 arc down across. The image was originally taken on February 5, 1995, for a total exposure time of 1.6 hours.

Named after American astronomer Edwin Hubble who was one of the first to study this nebula, this fan-shaped gas cloud is illuminated by the bright star R Monocerotis (R Mon) at the bottom of the nebula. Dense, moving concentrations of dust near the star cause the nebula to appear to change, as was first noted by Hubble.

The star itself cannot be seen directly - only through the nebula. It is believed to be at least 10 times the mass of the sun and be only 300,000 years old. There is probably a symmetrical counterpart to this nebula on the other side of the star, but if it exists, it is currently heavily obscured by the dust between us and it.

October's second Hubble Heritage image is of NGC 2346, a planetary nebula. 3,900 light-years from us, the NGC 2346 lies in the constellation Monoceros; this image covers approximately 2.8 arc minutes down, and the nebula is about 0.3 light-years in diameter. The image was originally taken on March 6, 1997, for a total exposure time of 24 minutes.

Most planetary nebulae seem only to possess one central star. NGC 2346, however, actually has a pair of very close stars in its center, orbiting each other every 16 days. It is believed that the binary system was originally more widely separated, but as the star responsible for the nebula expanded in size and lost much of its mass, the companion drifted closer towards the red giant.

Later, as the red giant evolved further and its core was exposed to space, the fast stellar wind emerged perpendicularly to the ring and inflated the two lobes of this nebula. It is this two-stage process that is believed to have resulted in the butterfly-like shape of the nebula.

NGC 2440 - Planetary Nebula October's third Hubble Heritage image is of NGC 2440, a planetary nebula. 3,600 light-years from us, NGC 2440 lies in the constellation Puppis; this image covers approximately 37 arcseconds down. The image was originally taken on November 18, 1995, for a total exposure time of 19 minutes.

This planetary nebula has a much more chaotic structure than most others (reference above October 1999 image). The central star in this nebula is about 200,000 K (360,000 °F) - one of the hottest known. The apparently random structure of this nebula suggests that there have been periodic, oppositely directed outflows from the star.

Rich in clouds of dust, some forming long, dark streaks away from the central star, this nebula fluoresces due to the ultraviolet radiation from the hot star. The nebula is actually surrounded by a much larger cloud of cooler gas, but it is invisible in optical light, but it is visible in infrared.

October's fourth Hubble Heritage image is of Herbig-Haro 32 (HH 32 for short), a Herbig-Haro Object. 960 light-years from us, HH 32 lies in the constellation Aquila; this image covers approximately 1.6 minutes down. The image was originally taken on August 25, 1994, for a total exposure time of 3.8 hour.

A Herbig-Haro Object is formed when young stars eject jets of material into interstellar space. This particular object is old enough to have already had the bright, central star clear much of the dust out of the central region, exposing the star to direct view.

Many young stars are surrounded by disks of dust and gas that form from the original nebula that gave rise to the star. Material from the disk gradually spirals towards the star and becomes part of it, but some of the material is ejected perpendicularly to the disk at speeds near 322 km per sec (200 miles per sec) and forms two oppositely directed jets. These jets plow their way into the surrounding nebula, producing shock waves that heat the gas and cause it to glow.

In this image, the colors have been coded so that hydrogen atoms are green, sulfur ions are blue, and several other atoms, ions, and radiation from the exiting star reflected by the surrounding gas is red. This glow is called a Herbig-Haro Object, in honor of the astronomers George Herbig and Guillermo Haro who did much of the early work in this area in the 1950's.

The jet on the top side is about 0.2 light-years from the star at its farthest extent, and is pointed nearly in our direction. The opposite jet on the bottom lies on the farther side of the star. It is fainter either because it is partially obscured by dust around the star or there is less material in front of the star. The jets in total are about 0.54 light-years in length.

November's Hubble Heritage image is of NGC 2207 and IC 2163, two merging galaxies. 114 million light-years from us, these lie in the constellation Canis Major; this image covers approximately 2.5 arcminutes down, and NGC 2207 (left) has a diameter of about 143,000 light-years and IC 2163 (right) has a diameter of about 101,000 light-years. The image was originally taken on May 25, 1996, and November 11, 1998, for a total exposure time of 4.5 hours.

These two interacting spiral galaxies are cataloged as NGC 2207 on the left and IC 2163 on the right. Strong tidal forces from the larger NGC 2207 have distorted the shape of IC 2163 and flung stars and gas out as long strings stretching a hundred thousand light-years towards the right edge of the image.

Computer simulations by a team lead by Bruce and Debra Elmegreen, Hubble images, and measurements made with the National Science Foundation's Very Large Array Radio Telescope in New Mexico reveal the motions of these galaxies and aid in the reconstruction of the collision. They indicate that IC 2163 is swinging by NGC 2207 in a counterclockwise direction, having made its closest approach about 40 million years ago. IC 2163 does not have enough energy to escape the gravitational pull of NGC 2207, and so it will eventually swing past the larger galaxy again in the future.

The high resolution of Hubble shows dust lanes in the larger galaxy's spiral arms, silhouetted against the background of IC 2163. It also shows parallel dust filaments extending along the tidal arms on the right side. The large amounts of dust and gas in both galaxies will probably launch a period of active star formation in the near future.

This image was created from three separate pointings of Hubble.

December's Hubble Heritage image is of star field in the Large Magellanic Cloud (LMC). 168,000 light-years from us, this star field lies in the constellation Dorado; this image covers approximately 2.7 arcminutes across (130 light-years). The image was originally taken on January 31 - February 1, 1996, for a total exposure time of 7 hours.

This star field image represents the deepest color picture ever obtained of an are of the LMC. Over 10,000 stars are visible in this image, the faintest being about 100,000,000 times dimmer than can be seen with the naked eye. If the sun were in this image, it would be one of those faintest stars.

Besides the myriad stars, sheets of glowing gas and dark patches of interstellar dust are visible in this portrait of part of a satellite galaxy, first discovered by Ferdinand Magellan, and one of the closest to our own Milky Way. The image is coded so that stars are approximately true-color, so that those with temperatures in excess of 10,000 K (18,000 °F) are blue-white and those cooler than 6,000 K (11,000 °F) are reddish.