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Hubble Heritage Archive - 2000 Hubble Heritage Archive: 1998 | 1999 | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 Gemini | Apollo | Hubble Space Telescope
Hubble Heritage Picture - January 2000
NGCis currently forming clusters of new stars from its vast clouds of gas and dust. Visible in this image are a myriad of faint stars - showing that star formation has been going on here for several billion years - but the picture is dominated by clouds of glowing gas surrounding bright stellar clusters. The youngest of the star clusters in in the lower right of the image, appearing as about a half-dozen bright clumps of glowing gas. Each cloud glows through a process called fluorescence: strong ultraviolet (UV) radiation emitted from the stars within it cause the atoms in the cloud to become stripped of at least one electron, ionizing the gas and causing it to glow. Hot, young stars are blue-white because of their high surface temperatures, which range from 10,000-50,000 K (18,000-90,000 °F). Besides the UV radiation emitted from the stars, high-velocity stellar winds moving at thousands of km per sec from the stars are also plowing through the surrounding gas, blowing bubbles throughout the nebular region. In the older clusters, such as to the lower left of the youngest, an obvious cavity can be seen around the cluster. Near the center of NGC 4214 lies a cluster of hundreds of massive blue stars, each over 10,000 times more luminous than the sun. A heart-shaped bubble surrounds the cluster, growing by the combined stellar winds of the stars and also supernovae from the massive stars as they end their lives. Hubble Heritage Picture - February 2000 February's Hubble Heritage image is of Keyhole Nebula within the Carina Nebula (NGC 3372), an emission nebula. 8,000 light-years from us, the Keyhole Nebula lies in the constellation Carina; this image covers approximately 3.8 arcminutes across. The image was originally taken on April 18, 1999, for a total exposure time of 1.7 hours. Dominated by a large, circular feature (which is part of the keyhole nebula), this celestial treat was named by the 19th century Sir John Herschel. Besides the Keyhole Nebula, the parent Carina Nebula contains several stars that are among the hottest and most massive known - about 10 times as hot (60,000 K (110,000 °F)) and 100 times as massive as the sun. The circular keyhole structure contains both bright filaments of hot, fluorescing gas, and dark silhouetted clouds of cooler molecules and dust - all in rapid and chaotic motion. Hubble's high resolution is able to show relative three-dimensional locations of many of the features of this nebula, including several small, dark globs that may be in the process of collapsing into new stars. The two large dust clouds located near the bottom center and upper left edges of the image contain pillars and knobs. These appear to point toward a luminous, massive star located outside the image further up and left, which may be responsible for illuminating and sculpting them by means of its radiation and stellar wind. If sufficiently dense, these dark clouds may collapse into small star clusters. Otherwise they will evaporate. The Carina Nebula has an overall diameter of more than 200 light-years and the diameter of the keyhole ring is about 7 light-years. Hubble Heritage Picture - March 2000
NGC 1999 was discovered about 200 years ago by Sir William Herschel and his sister, Caroline, and was later cataloged in the 19th century New General Catalogue as object 1999. It is an ideal example of a reflection nebula - a nebula that shines because light from an embedded star illuminates its dust, for it does not produce any visible light of its own. NGC 1999 is also important because the first Herbig-Haro object - objects known to be jets of gas ejected from very young stars - was discovered just next to it. The source of illumination for this nebula is the bright, young star that is visible in the left portion of this image. The star is cataloged as V380 Orionis and it is bluish-white due to its high surface temperatures of about 10,000 K (18,000 °F). Its mass is about 3.5 that of our sun's. The reflection nebula is actually its parent nebula, out of which the star collapsed. The large "T"-shaped, black cloud near the center is an example of a Bok globule, named for the former University of Arizona astronomer Bart Bok. The cloud is made of cold gas and dust which is so dense that it blocks all of the light behind it. The globule is in front of the reflection nebula. Astronomers believe that new stars may be forming inside Bok globules through gravitational contraction. Hubble Heritage Picture - April 2000 April's Hubble Heritage image is of NGC 6751, a planetary nebula. 6,500 light-years from us, NGC 6751 lies in the constellation Aquila; this image covers approximately 24 arcseconds across (0.8 light-years). The image was originally taken on April 21, 1998, for a total exposure time of 30 minutes. A cloud of material ejected from the hot, former sun-like star in its center thousands of years ago, this planetary nebula is one of the more unusual, presenting several poorly understood features. Blue areas are the hottest glowing gas, which forms a circular ring around the central stellar remnant. Orange and red colors show cooler gas, which tends to lie in long streamers pointing away from the central star. The origin of these cooler clouds is uncertain, but the streamers are evidence that the shapes are affected by radiation and stellar winds from the central star, which has a surface temperature estimated at 140,000 K (250,000 °F). The nebula is expanding at about 40 km per sec (25 miles per sec), and over the course of a few years, follow-up observations should reveal a slight increase in the nebula's size. This measurement will allow a more accurate distance measurement to the nebula. Hubble Heritage Picture - May 2000
This Hubble Heritage image presents a very chance alignment of a face-on spiral galaxy lying precisely in front of another large spiral galaxy. This provides astronomers with a rare chance to visualize dark material within the front galaxy, visible because it blocks the light of the galaxy behind it. This dark dust lying in the spiral arms of the foreground galaxy stands out against the brightness of the background galaxy. It shows where the interstellar dust clouds are located and how much light they absorb. The bright blue stars near the center of the NGC 3314a formed recently. In many galaxies, interstellar dust lies only in the same regions as recently formed blue stars, but there are numerous additional dark dust lanes not associated with any bright young stars. The small, red patch near the center of the image is the nucleus of NGC 3314b. It appears reddened because its light has passed through the dust of the foreground galaxy; the same process that makes the sun appear red at sunset and sunrise. Hubble Heritage Picture - June 2000 June's Hubble Heritage image is of NGC 1953, AKA the Crab Nebula, a supernova remnant. 6,500 light-years from us, the Crab Nebula lies in the constellation Taurus; this image covers approximately 1.6 arcminutes across (3.0 light-years). The image was originally taken in January 1995, and April 1995, for a total exposure time of 10 hours. On June 4, 1054 A.D., Chinese astronomers discovered the appearance of a new star that was so bright it was visible during daylight for several weeks. Native Americans also documented this feature in rock paintings in the southwestern United States. In current times, all that remains of this supernova is the Crab Nebula remnant. The original star that exploded nearly a millennia ago began its life with a mass about 10 times the sun's. Such a large star lives only about 50 million years before exploding. This Hubble image reveals the Crab Nebula in unprecedented detail. In this image, the ragged shreds of gas are expanding from the explosion center at over 4.8 million km per hour (3 million mph). At the center there now exists a pulsar, visible in the image as the lower of two moderately bright stars to the upper left of center. The pulsar weighs in at about 1.4 solar masses, but it is only 16 km (10 miles) in diameter. It has a rotation rate of 30 times per second. The pulsar heats the surrounding gas and dust, creating the nebula's glow. The nebula is colored so that hydrogen is orange, nitrogen is red, sulfur is pink, and oxygen is green. The color shades represent the temperature and density variations in the gas. Hubble Heritage Picture - July 2000
About to get a ticket for breaking the cosmic speed limit, the particles in the jet that is streaming from the center of this galaxy are moving at nearly the speed of light. The jet was noted as early as 1918 by astronomer H. D. Curtis, who saw a "straight ray" protruding from M87. When the filed of radio astronomy was gaining a foothold in the 1950's, Virgo A was one of the brightest radio sources in the sky, and it was found to be associated with M87 and its jet. The massive jet is supported by a black hole in the galaxy's center. This supermassive black hole weighs in at about 2 billion solar masses. The jet originates from this due to the disk of gas orbiting the black hole and is propelled and concentrated by the huge magnetic fields trapped within. The light seen is produced by electrons that are twisting along the magnetic field lines of the jet in a process known as "synchrotron radiation," and this also gives the jet its bluish hue. Giant jets powered by massive black holes are not rare, but M87 is the nearest and most well-studied. Hubble Heritage Picture - August 2000 August's Hubble Heritage image is of M15, AKA NGC 7078, a globular cluster. 40,000 light-years from us, M15 lies in the constellation Pegasus; this image covers approximately 86.5 arcseconds down (17 light-years). The image was originally taken in December 1998, for a total exposure time of 3.7 hours. This conglomeration of hundreds of thousands of stars is shown in approximately true colors. The brightest stars are red giants, some with an orange color that are hotter than the red ones. Most of the stars are hotter, shining as bluish-white. But not everything in this nebula is characteristic of globular clusters. In the upper left of this image resides a pinkish object that is a gas cloud surrounding a dying star. Known as Kuestner 648 (K 648 for short), this was the first planetary nebula to be identified in a globular cluster. It was first identified in 1928 by F. G. Pease, who was working at the 100-inch telescope of the Mount Wilson Observatory. Since then, only three other planetary nebulae have been found in globular clusters. The surface temperature of the central star in K 648 is about 40,000 K (70,000 °F). Hubble data show that the star's remaining mass is about 60% that of our sun. The outer layers were ejected about 4,000 years ago. The reason that this is so odd is most stars remaining in the globular cluster have about 80% the sun's mass. Astronomers believe that stars such as these will not evolve planetary nebulae. The Hubble images of this were used to test a theory that the original star that spawned the nebula was part of a close binary system and it stole mass off its companion. No companion was found. Thus, the mystery still remains, although the binary hypothesis could be true if the two stars actually merged. Hubble Heritage Picture - September 2000
A few thousand years ago, the star at the heart of the Spirograph Nebula was a red giant. It then began to eject its outer layers into space to form the nebula, which has now expanded to a diameter of about 13,000 A.U. The hot core of the former red giant remains, spreading ultraviolet radiation which causes the surrounding gas to fluoresce. The nebula will gradually disperse into interstellar space over the next several thousand years. This is also the fate of our own star in about 5 billion years. The image has been color coded so that ionized nitrogen (coolest) is red, hydrogen is green, and ionized oxygen (hottest) is blue. The textures seen in the nebula were hitherto unknown until Hubble took this image, and their origin is still uncertain. Hubble Heritage Picture - October 2000 October's Hubble Heritage image is of SMC-N 81, a star-forming region in the Small Magellanic Cloud (SMC). 200,000 light-years from us, SMC-N 81 lies in the constellation Tucana; this image shows the object to be about 12 arcseconds (12 light-years) in diameter. The image was originally taken on September 4, 1997, for a total exposure time of 1.5 hours. The massive, recently formed stars inside this nursery are loosing mass at a high rate through strong stellar winds and shock waves. The two most luminous stars, seen in this image as a very close pair near the center of the image, emit a lot of ultraviolet radiation, causing the nebula to fluoresce - glow. Outside the glowing gas is cooler material made of hydrogen molecules and dust. It is normally invisible, but some of it is seen silhouetted against the nebula as dust lanes and a dark, elliptical knot. Before Hubble, no ground-based telescope was able to determine if the nebula contained one star, a few stars, or many stars. Hubble cleared that matter, showing that the last case exists. This information is very important for theories of star formation, and N 81 offers an opportunity for a close-up of the turbulent conditions that accompany the birth of massive stars. The brightest stars here have a luminosity of 300,000 times the sun's. Especially interesting to astronomers is to study star formation in the SMC because its chemical composition is different from our own galaxy's. All the chemical elements, other than hydrogen and helium, have only 1/10 the abundance seen in our own galaxy. Thus, it is a guide for studying the star formation that occurred in the ancient universe, still visible in far-off galaxies, before nuclear processes in stars had synthesized the elements heavier than helium Hubble Heritage Picture - November 2000
Millions of years ago, the two galaxies that are visible in this image actually collided. The bright blue-white stream passing from the large spiral galaxy with its nucleus still intact shows the path of the smaller galaxy (nearly out of the image). Galaxy collisions rarely actually result in star collisions due to the vast amounts of space between each relatively tiny star (the radius of our sun is about 0.000002% the distance to the closest star, Proxima Centauri). However, the vast clouds of interstellar gas and dust that float through galaxies often collide. High relative velocities increase pressure in the clouds, causing densities to rise and star formation to start, as evidenced by the hot blue stars visible throughout much of this image. Hubble Heritage Picture - December 2000 December's Hubble Heritage image is of IC 349, AKA Barnard's Merope Nebula, a reflection nebula in the Pleiades. 380 light-years from us, IC 349 lies in the constellation Taurus; this image covers approximately 0.05 light-years across. The image was originally taken on September 19, 1999, for a total exposure time of 18.3 minutes. One of the brightest stars in the Pleiades cluster is Merope, and it lies about 0.06 light-years to the upper right of the nebula, just outside this image. The close passage of that star is both destroying the nebula and lighting it; the reflected starlight off the nebula is what classifies it as a "reflection nebula." This nebula is named after its discoverer, American astronomer E. E. Barnard, who found it in 1890 with the Lick Observatory's 36-inch telescope. In most cases, the nebulae that surround star clusters are parents to those clusters; the Pleiades is a different case, where the nebula is an independent cloud that is drifting through the cluster at a relative speed of 11 km per sec (6.8 miles per sec). The colorful light rays in the upper right point to Merope, but they are an artifact of the telescope. However, the parallel features that are reaching for the star, coming out of the nebula, are real, and were previously unknown to exist. Astronomers George Herbig and Theodore Simon of the University of Hawaii propose that the radiation pressure from Merope is what causes the tendrils. This works by the phenomenon where light shining on dust particles can act to decelerate them. Smaller particles are slowed more than larger, heavier ones. Thus, this relative sorting is what we are seeing: The heaviest particles are closest to the star because they have decelerated the least, while the lightest particles are remaining farther away. Over the next several thousand years, the nebula - if it survives the close passage with Merope without being destroyed - will move on, somewhat like a comet swinging past our Sun. This chance collision allows astronomers to study interstellar material under very rare conditions, and thus learn more about the structure of the dust lying between stars. 
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January's
Hubble Heritage image is of NGC 4214, a galaxy with bright star-forming regions.
13 million 
March's
Hubble Heritage image is of NGC 1999, a 
May's
Hubble Heritage image is of NGC 3314a (foreground) and NGC 3314b (background,
a back-lit galaxy pair
July's
Hubble Heritage image is of M87, AKA NGC 4486, AKA Virgo A, a giant elliptical
galaxy. 50 million light-years from us, M87 lies in the constellation Virgo;
this image covers approximately 31 arcseconds across (7,500 light-years)
- the length of the jet in optical wavelengths is 5,000 light-years; in radio
wavelengths it is 100,000 light-years long. The image was originally taken
in February 1998, for a total exposure time of 55 minutes.
September's
Hubble Heritage image is of IC 418, AKA the Spirograph Nebula, a 
November's
Hubble Heritage image is of NGC 6745, an interacting galaxy. 206 million
light-years from us, NGC 6782lies in the constellation Lyra; this image shows
the galaxy system to be about 1.5x0.7 arcminutes in dimensions, with the
semi-major axis at roughly 85,000 light-years. The image was originally taken
on March 18-21, 1996, for a total exposure time of 10.3 hours.