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Hubble Heritage Archive - 2006 Hubble Heritage Archive: 1998 | 1999 | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 Gemini | Apollo | Hubble Space Telescope
January 2006 January's Hubble Heritage image is of the emission nebula M42, AKA The (Great) Orion Nebula. 1,500 light-years from us, the nebula lies in the constellation Orion. The image is combined from data taken in October 2004 through April 2005. This image is a composite of five filters (B (F435W), V (F555W), H-α (F658N), i (F775W), and z (F850LP)). Close inspection of the 2006 Hubble Space Telescope color mosaic of the Orion Nebula reveals numerous treasures that reside within the nearby, intense star-forming region. Southwest of the Trapezium stars located in the center of the nebula, this sub-frame is a stunning Hubble Heritage portrait captures a variety of intricate objects. Deeply contrasting areas of light and dark blend with a palette of colors mix to form rich swirls and fluid motions that would make even the best artists stand back and admire their work. Visible slightly above left center is the star LL Orionis (LL Ori), originally released by the Hubble Heritage Project in 2002. The delicate bow shock that surrounds LL Ori points towards the stream of gas flowing slowly away from the center of the Orion Nebula, near the Trapezium stars located off the image to the upper left. Close examination of the ends of the bow shock show secondary shocks that are formed as a two-sided jet of gas flowing away from this forming star at high velocity strikes the stream of low velocity gas from the center. To the right of LL Ori, a ghostly veil of material hangs thick and dark, obscuring portions of the nebula behind it. The bright star toward the lower left of the image, known as LP Orionis (LP Ori), is surrounded by a prominent reflection nebula. Astronomers believe the star is moving within another veil of material that lies in front of M42. The appearance of the bright rim above LP Ori indicates that the teardrop shaped dark region around the illuminating star must be a cavity formed as the star moves through the veil material, rather than being a dusty veil obscuring light behind it. February 2006
Recent observations of this galaxy taken in visible and infrared light come together in a colorful depiction of many of the galaxy's features. Bright blue areas of star formation pepper the spiral arms, while ruddy dust lanes follow the spiral structure into a yellowish central nucleus of older stars. The image is complemented by myriad far-off background galaxies. However, this galaxy image is more than just a pretty picture. It is helping astronomers to more accurately measure the expansion rate of the universe. NGC 1309 was home to supernova SN 2002fk, whose light reached Earth in September 2002. This supernova event, known as a Type Ia, resulted from a white dwarf star accreting matter from its companion in a binary star system. When the white dwarf collected enough mass and was no longer able to support itself, the star detonated, becoming the brightest object in the galaxy for several weeks. Nearby Type Ia supernovae like SN 2002fk in NGC 1309 are used by astronomers to calibrate distance measures in the universe. By comparing nearby type Ia supernovae to more distant ones, they can determine not only that the universe is expanding, but that this expansion is accelerating. However, this method only works if the distance to the host galaxies is known extremely well. That's where the Hubble Telescope comes into play. Since NGC 1309 is relatively close to us, the high resolution of Hubble's Advanced Camera for Surveys can help accurately determine the distance to the galaxy by looking at the light output of a particular type of variable star called a Cepheid variable. Cepheids are well studied in our own galaxy, and are known to vary regularly in brightness. By studying the Cepheids in NGC 1309, astronomers are able to accurately measure the distance to NGC 1309, and thus, to SN 2002fk. The expansion of the universe was discovered by Edwin Hubble, the Hubble Space Telescope's namesake, nearly a century ago, but the accelerating expansion is a recent discovery which has interesting consequences for cosmological models. March 2006 March's Hubble Heritage image is of the spiral galaxy M101, AKA NGC 4547, AKA The Pinwheel Galaxy. 25 million light-years from us, the galaxy lies in the constellation Ursa Major. The image is combined from data taken November 13-16, 2002, for 6.5 hours. This image is a composite of three filters (B (F435W), V (F606W), I (F814W)). A close cropping of spiral galaxy M101 shows an array of stunning details never-before-seen in this galaxy. Due to the high sensitivity and fine resolution of Hubble's Advanced Camera for Surveys (ACS), individual dust lanes in the spiral arms are as clearly visible as rivers flowing through a mountain range here on Earth taken from an aerial photo. Bright, hot regions that are areas of active star formation also dot the spiral arms, akin to ground photos of the bright lights of major cities when photographed at night. Several bright stars appear in this small section of M101. They are in our own galaxy, superimposed in the line of sight and appear much brighter than the stars within M101 because they are so much closer. So too, a background spiral galaxy, millions of light-years behind M101, appears between two spiral arms. The bright nucleus of M101 just off to the upper left appears brighter and redder than the rest of the galaxy seen in the image. Stars near the halo that surround the nucleus are older and redder compared to the blue, young, hot stars that delineate the spiral arms and populate the metropolitan-style star-forming regions. This image is a portion of the of a much larger mosaic of M101, created by combining Hubble data with ground-based images of the galaxy where Hubble data is not available. This cropping contains only Hubble ACS data from blue, green and infrared filters taken in November 2002. April 2006
The yearly ritual of spring cleaning clears a house of dust as well as dust "bunnies," those pesky dust balls that frolic under beds and behind furniture. NASA's Hubble Space Telescope has photographed similar dense knots of dust and gas in our Milky Way Galaxy. This cosmic dust, however, is not a nuisance: It is a concentration of elements that are responsible for the formation of stars in our galaxy and throughout the universe. These opaque, dark knots of gas and dust are called "Bok globules," and they are absorbing light in the center of the nearby emission nebula and star-forming region, NGC 281. The globules are named after astronomer Bart Bok, who proposed their existence in the 1940's. Bok hypothesized that giant molecular clouds, on the order of hundreds of light-years in size, can become perturbed and form small pockets where the dust and gas are highly concentrated. These small pockets become gravitationally bound and accumulate dust and gas from the surrounding area. If they can capture enough mass, they have the potential of creating stars in their cores; however, not all Bok globules will form stars, since some will dissipate before they can collapse to form stars. That may be what's happening to the globules seen here in NGC 281. Near the globules are bright blue stars, members of the young open cluster IC 1590. The cluster is made up of a few hundred stars. The cluster's core, off the image towards the top, is a tight grouping of extremely hot, massive stars with an immense stellar wind. The stars emit visible and ultraviolet light that energizes the surrounding hydrogen gas in NGC 281. This gas then becomes super heated in a process called ionization, and it glows pink in the image. The Bok globules in NGC 281 are located very close to the center of the IC 1590 cluster. The exquisite resolution of these Hubble observations shows the jagged structure of the dust clouds as if they are being stripped apart from the outside. The heavy fracturing of the globules may appear beautifully serene but is in fact evident of the harsh, violent environment created by the nearby massive stars. The Bok globules in NGC 281 are visually striking nonetheless. They are silhouetted against the luminous pink hydrogen gas of the emission nebula, creating a stark visual contrast. The dust knots are opaque in visual light. Conversely, the nebulous gas surrounding the globules is transparent and allows light from background stars and even background galaxies to shine through. May 2006 May's Hubble Heritage image is of the starburst galaxy M82, AKA NGC 3034, AKA The Cigar Galaxy. 12 million light-years from us, the galaxy lies in the constellation Ursa Major; this image covers approximately 7.9 arcminutes across (28,000 light-years). The image is combined from data taken March 27-29, 2006, for a total of 13.7 hours. This image is a composite of four filters (B (F435W), V (F555W), H-α (F658N), and I (F814W)). To celebrate the Hubble Space Telescope's 16 years of success, the two space agencies involved in the project, NASA and the European Space Agency (ESA), are releasing this image of the magnificent starburst galaxy, Messier 82 (M82). This mosaic image is the sharpest wide-angle view ever obtained of M82. The galaxy is remarkable for its bright blue disk, webs of shredded clouds, and fiery-looking plumes of glowing hydrogen blasting out of its central regions. Throughout the galaxy's center, young stars are being born 10 times faster than they are inside our entire Milky Way Galaxy. The results in huge concentration of young stars carved into the gas and dust at the galaxy's center. The fierce galactic superwind generated from these stars compresses enough gas to make millions of more stars. In M82, young stars are crammed into tiny but massive star clusters. These, in turn, congregate by the dozens to make the bright patches, or "starburst clumps," in the central parts of M82. The clusters in the clumps can only be distinguished in the sharp Hubble images. Most of the pale, white objects sprinkled around the body of M82 that look like fuzzy stars are actually individual star clusters about 20 light-years across and containing up to a million stars. The rapid rate of star formation in this galaxy eventually will be self-limiting. When star formation becomes too vigorous, it will consume or destroy the material needed to make more stars. The starburst then will subside, probably in a few tens of millions of years. June 2006
Hubble's sharp vision reveals a crisp dust lane dividing this galaxy into two halves. The image highlights the galaxy's structure: a subtle, reddish bulge surrounding a bright nucleus, a blue disk of stars running parallel to the dust lane, and a transparent outer halo. Some faint, wispy trails of dust can be seen meandering away from the disk of the galaxy out into the bulge and inner halo. The outer halo is dotted with numerous gravitationally bound clusters of nearly a million stars each, known as globular clusters. Background galaxies that are millions to billions of light-years farther away than NGC 5866 are also seen through the halo. NGC 5866 is a disk galaxy of type "S0" (pronounced s-zero). Viewed face on, it would look like a smooth, flat disk with little spiral structure. It remains in the spiral category because of the flatness of the main disk of stars as opposed to the more spherically rotund (or ellipsoidal) class of galaxies called "ellipticals." Such S0 galaxies, with disks like spirals and large bulges like ellipticals, are called "lenticular" galaxies. The dust lane is slightly warped compared to the disk of starlight. This warp indicates that NGC 5866 may have undergone a gravitational tidal disturbance in the distant past, such as by a close encounter with another galaxy. This is feasible because it is the largest member of a small cluster known as the NGC 5866 group of galaxies. The starlight disk in NGC 5866 extends well outside the dust absorption. This means that dust and gas still in the galaxy and potentially available to form stars does not stretch nearly as far out in the disk as it did when most of these stars in the disk were formed. The Hubble image shows that NGC 5866 shares another property with the more gas-rich spiral galaxies: Numerous filaments that reach out perpendicular to the disk punctuate the edges of the dust lane. These are short-lived on an astronomical scale, since clouds of dust and gas will lose energy to collisions among themselves and collapse to a thin, flat disk. For spiral galaxies, the incidence of these fingers of dust correlates well with tracers of how many stars have been formed recently, for massive stars' energy input moves gas and dust around to create these structures. The thinness of dust lanes in S0s has been discussed in ground-based galaxy atlases, but it took the resolution of Hubble to show that they can have their own smaller fingers and chimneys of dust. NGC 5866 has a diameter of roughly 60,000 light-years (18,400 parsecs) - only two-thirds the diameter of the Milky Way - although its mass is similar to our galaxy. July 2006 July's Hubble Heritage image is of the supernova remnant E0102. 210 thousand light-years from us, the remnant lies in the constellation Tucana; this image covers approximately 3.0 arcminutes across (180 light-years). The image is combined from data taken October 15/16, 2003, and July 4, 1995, for a total of 4.2 hours. This image is a composite of five filters (B (F475W), V (F550MW), H-α (F658N), O III (F502N), and i (F775W)). The supernova remnant (SNR), known as "E0102" for short, is the greenish-blue shell of debris just below the center of the Hubble image. Its name is derived from its cataloged placement (or coordinates) in the celestial sphere. More formally known as 1E0102.2-7219, it is located almost 50 light-years (15 parsecs) away from of the edge of the massive star-forming region, N 76, also known as Henize 1956 in the Small Magellanic Cloud. This delicate structure glowing a multitude of lavenders and peach hues, resides in the upper right of the image. The composition, and thus, the coloring of the diffuse remnant in comparison to its star-forming neighbor is due to the presence of very large quantities of oxygen compared to hydrogen. E0102 is a member of the oxygen-rich class of SNRs showing strong oxygen and other more metal-like abundances in its optical and X-ray spectra, and an absence of hydrogen and helium. N 76 in contrast is made up primarily of glowing hydrogen emission. One explanation for the abundance of oxygen in the SNR is that the parent star was very large and old, and it had blown away most its hydrogen as stellar wind before it exploded. It is surmised that the progenitor star that caused the supernova explosion may have been a Wolf-Rayet. These stars, which can be upward of 20 times the mass of the sun and tens of thousands times more luminous, are famous for having a strong stellar wind throughout their lifetime. This stellar wind carried off material from the outer-most shells of the star (the hydrogen and helium shells), leaving the next most abundant element, oxygen, as a visible signature after the star exploded as a supernova. Determined to be only about 2000 years old, E0102 is relatively young on astronomical scales and is just beginning its interactions with the nearby interstellar medium. Young supernova remnants like E0102 allow astronomers to examine material from the cores of massive stars directly. This in turn gives insight on how stars form, their composition, and the chemical enrichment of the surrounding area. As well, young remnants are a great learning tool to better understand the physics of supernova explosions. August 2006
N180B is an active region of star formation in the irregular galaxy, the Large Magellanic Cloud (LMC). This particular region within the LMC contains some of the brightest clusters of stars known to exist. These clusters are known as "OB associations" because they contain stars of class O and class B, two of the brightest and hottest classes of stars. Class O stars can be more than a million times brighter than our Sun. The expected lifetime of an O star is relatively short, on the order of only a few million years, while stars similar in luminosity and temperature of the Sun can live for tens of billions of years. The presence of the hottest O stars in N180B indicates that even the most massive stars have remained intact. This in turn suggests that the star-forming region is young and has probably not hosted any supernova explosion. The hot O stars in the clusters are extremely luminuous. Their energy output causes a radiation pressure that leads to incredibly strong stellar winds. These stellar winds have the ability to disperse gas across hundreds of light-years as well as form dense dust clouds, both of which are evident in N180B. N180B and other similar star-forming regions are collectively known as H II (pronounced "H-two") regions because of the presence of excited hydrogen gas. In the case of N 180B, there is a combination of hydrogen and oxygen gas, with the brighter areas a contribution of the hydrogen. There are 100 light-year-long dust streamers that run the length of the HII region as well as smaller, more compact dust clouds and elephant trunks. If the pressure from ambient interstellar gas is high enough, star formation might be triggered in these small dust clouds. The fact that these small dust clouds embedded in the ionized gas exist at all is more evidence that this is still a young star-formation region.
Cas A is the youngest known remnant from a supernova explosion in the Milky Way, and the new Hubble image shows the complex and intricate structure of the star's shattered fragments. The image is a composite made from 18 separate images, and it shows the Cas A remnant as a broken ring of bright filamentary and clumpy stellar ejecta. These huge swirls of debris glow with the heat generated by the passage of a shockwave from the supernova blast. The various colors of the gaseous shards indicate differences in chemical composition. Bright green filaments are rich in oxygen, red and purple are sulfur, and blue are composed mostly of hydrogen and nitrogen. A supernova such as the one that resulted in Cas A is the explosive demise of a massive star that collapses under the weight of its own gravity. The collapsed star then blows its outer layers into space in an explosion that can briefly outshine its entire parent galaxy. Cas A is relatively young, estimated to be only about 340 years old. Hubble has observed it on several occasions to look for changes in the rapidly expanding filaments. In the latest observing campaign, two sets of images were taken, separated by nine months. Even in that short time, Hubble’s razor-sharp images can observe the expansion of the remnant. Comparison of the two image sets shows that a faint stream of debris seen along the upper left side of the remnant is moving with high speed - up to 31 million miles per hour (fast enough to travel from Earth to the Moon in 30 seconds!). Supernova explosions are the main source of elements more complex than oxygen, which are forged in the extreme conditions produced in these events. The analysis of such a nearby, relatively young and fresh example is extremely helpful in understanding the evolution of the universe. 
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August's Hubble
Heritage image is of a section of a nebula called LMC N180B in the Large
Magellanic Cloud. 160 thousand light-years from
us, the nebula lies in the constellation Dorado; this image covers
approximately 2.5 arcminutes across (180 light-years). The image is
combined from data taken April 29, 1998, for a total
of 37 minutes. This image is a composite of two filters (H-
Also
released this month is the supernova remnant known as Cassiopeia A (often
abbreviated as Cas A).
10,000 light-years from us, the remnant lies in the constellation
Cassiopeia; this image covers approximately 8.5 arcminutes across (25 light-years).
The image is combined from data taken in March and December of 2004, for
a total of 2.3 days' worth of exposure time. This image is a composite of
three filters (R (F625W), i (F775W), and z (F850LP)).