Hubble Captures Collision of Gases Near Dying Star

Hubble Captures Collision of Gases Near Dying Star This colorful image from the Hubble Space Telescope shows the collision of two gases near a dying star. Astronomers have dubbed the tadpole-like objects in the upper right-hand corner "cometary knots" because their glowing heads and gossamer tails resemble comets. Although astronomers have seen gaseous knots through ground-based telescopes, they have never seen so many in a single nebula. Hubble captured thousands of these knots from a doomed star in the Helix nebula, the closest planetary nebula to Earth at 450 light-years away in the constellation Aquarius. Each gaseous head is at least twice the size of our solar system; each tail stretches 100 billion miles, about 1,000 times the Earth's distance to the Sun. The most visible gaseous fragments lie along the inner edge of the star's ring, trillions of miles from the star at its center. The comet-like tails form a radial pattern around the star like the spokes on a wagon wheel. Astronomers have seen the spoke pattern using ground-based telescopes, but Hubble reveals for the first time the sources of these objects. Astronomers theorize that the gaseous knots are the results of a collision between gases. The doomed star spews the hot gas from its surface, which collides with the cooler gas that it had ejected 10,000 years before. The crash fragments the smooth cloud surrounding the star into smaller, denser finger-like droplets, like dripping paint. Astronomers expect the gaseous knots, each several billion miles across, to eventually dissipate into the cold blackness of interstellar space. This image was taken in August, 1994 with Hubble's Wide Field Planetary Camera 2. The red light depicts nitrogen emission ([NII] 6584A); green, hydrogen (H-alpha, 6563A); and blue, oxygen (5007A). Credit: C. Robert O'Dell and Kerry P. Handron (Rice University), NASA

Firestorm of Star Birth Seen in a Local Galaxy This festively colorful nebula, called NGC 604, is one of the largest known seething cauldrons of star birth in a nearby galaxy. NGC 604 is similar to familiar star-birth regions in our Milky Way galaxy, such as the Orion Nebula, but it is vastly larger in extent and contains many more recently formed stars. This monstrous star-birth region contains more than 200 brilliant blue stars within a cloud of glowing gases some 1,300 light-years across, nearly 100 times the size of the Orion Nebula. By contrast, the Orion Nebula contains just four bright central stars. The bright stars in NGC 604 are extremely young by astronomical standards, having formed a mere 3 million years ago. Most of the brightest and hottest stars form a loose cluster located within a cavity near the center of the nebula. Stellar winds from these hot blue stars, along with supernova explosions, are responsible for carving out the hole at the center. The most massive stars in NGC 604 exceed 120 times the mass of our Sun, and their surface temperatures are as hot as 72,000 degrees Fahrenheit (40,000 Kelvin). Ultraviolet radiation floods out from these hot stars, making the surrounding nebular gas fluoresce. NGC 604 lies in a spiral arm of the nearby galaxy M33, located about 2.7 million light-years away in the direction of the constellation Triangulum. M33, a member of the Local Group of galaxies that also includes the Milky Way and the Andromeda Galaxy, can be seen easily with binoculars. NGC 604 itself can be seen with a small telescope, and was first noted by the English astronomer William Herschel in 1784. Within our Local Group, only the Tarantula Nebula in the Large Magellanic Cloud exceeds NGC 604 in the number of young stars, even though the Tarantula Nebula is slightly smaller in size. NGC 604 provides Hubble astronomers with a nearby example of a giant star-birth region. Such regions are small-scale versions of more distant "starburst" galaxies, which undergo an extremely high rate of star formation. Starbursts are believed to have been common in the early universe, when the star-formation rate was much higher. Supernovae exploding in these galaxies created the first chemical elements heavier than hydrogen and helium. The image of NGC 604 was assembled from observations taken with Hubble's Wide Field Planetary Camera 2 in 1994, 1995, and 2001. Color filters were used to isolate light emitted by hydrogen, oxygen, nitrogen, and sulfur atoms in the nebula and ultraviolet, visible and infrared light from the stars within NGC 604 and the nearby spiral arms of M33. Image processors from the Hubble Heritage team at the Space Telescope Science Institute combined these various filter images to create this color picture. Image Credit: NASA and The Hubble Heritage Team (AURA/STScI) Acknowledgment: D. Garnett (U. Arizona), J. Hester (ASU), and J. Westphal (Caltech)

Hubble Telescope Photo Reveals Stellar Death Process This NASA Hubble Space Telescope image of planetary nebula NGC 7027 shows remarkable new details of the process by which a star like the Sun dies. New features include: faint, blue, concentric shells surrounding the nebula; an extensive network of red dust clouds throughout the bright inner region; and the hot central white dwarf, visible as a white dot at the center. The nebula is a record of the star's final death throes. Initially the ejection of the star's outer layers, when it was at its red giant stage of evolution, occurred at a low rate and was spherical. The Hubble photo reveals that the initial ejections occurred episodically to produce the concentric shells. This culminated in a vigorous ejection of all of the remaining outer layers, which produced the bright inner regions. At this later stage the ejection was non-spherical, and dense clouds of dust condensed from the ejected material. The results are being presented by astronomers Howard Bond, Karen Schaefer, and Laura Fullton of the Space Telescope Science Institute, and Robin Ciardullo of Pennsylvania State University, at the 187th meeting of the American Astronomical Society in San Antonio, Texas. "When we saw the Hubble photograph of the nebula NGC 7027, we were astounded by the exquisite wealth of detail that nobody had ever seen before," said Bond. The photograph was taken as part of a survey of planetary nebulae, which are clouds of gas and dust ejected from a star with a mass similar to that of the Sun as it reaches the end of its life. NGC 7027 is located about 3,000 light-years from Earth in the direction of the summer constellation Cygnus. When a star like the Sun nears the end of its life, it expands to more than 50 times its original diameter, becoming a red giant star. Then its outer layers are ejected into space, exposing the small, extremely hot core of the star, which cools off to become a white dwarf. Although stars like the Sun can live for up to 10 billion years before becoming a red giant and ejecting a nebula, the actual ejection process takes only a few thousand years. The NGC 7027 photograph is a composite of two Hubble images, taken in visible and infrared light, and is shown in "pseudo-color." Credit: H. Bond (STScI) and NASA

Hubble Photographs Turbulent Neighborhood Near Eruptive Star A small portion of the rough-and-tumble neighborhood of swirling dust and gas near one of the most massive and eruptive stars in our galaxy is seen in this NASA Hubble Space Telescope image. This close-up view shows only a three light-year-wide portion of the entire Carina Nebula, which has a diameter of over 200 light-years. Located 8,000 light-years from Earth, the nebula can be seen in the southern sky with the naked eye. Dramatic dark dust knots and complex structures are sculpted by the high-velocity stellar winds and high-energy radiation from the ultra-luminous variable star called Eta Carinae, or Eta Car (located outside the picture). This image shows a region in the Carina Nebula between two large clusters of some of the most massive and hottest known stars. The filamentary structure is caused by turbulence in the circumstellar gas, which in turn was caused by several stars shedding their outer layers. Cold gas mixes with hot gas, leaving a veil of denser, opaque material in the foreground. The chemical elements in the surroundings create a potential reservoir for new star formation. Areas in the brightest parts of the image at the top show elephant-trunk shaped dust clouds that may form into embryonic solar systems. This Hubble image was taken in July 2002 as part of a parallel observing program. The Hubble telescope has several instruments that can be simultaneously used to look at slightly different portions of the sky. In this case, the Space Telescope Imaging Spectrograph was used to study Eta Carinae itself, while the Wide Field Planetary Camera 2 was used to take this image of the nebulosity near Eta Car. This parallel observing mode increases Hubble's efficiency and allows astronomers to probe parts of the sky that they would not otherwise be able to investigate. Produced by the Hubble Heritage team, this color image is a composite of ultraviolet, visible, and infrared filters that have been assigned the colors blue, green, and red, respectively. Image Credit: NASA and The Hubble Heritage Team (AURA/STScI) Acknowledgment: S. Casertano (STScI)

Hubble Finds an Hourglass Nebula Around a Dying Star This is an image of MyCn18, a young planetary nebula located about 8,000 light-years away, taken with the Wide Field and Planetary Camera 2 (WFPC2) aboard NASA's Hubble Space Telescope (HST). This Hubble image reveals the true shape of MyCn18 to be an hourglass with an intricate pattern of "etchings" in its walls. This picture has been composed from three separate images taken in the light of ionized nitrogen (represented by red), hydrogen (green), and doubly-ionized oxygen (blue). The results are of great interest because they shed new light on the poorly understood ejection of stellar matter which accompanies the slow death of Sun-like stars. In previous ground-based images, MyCn18 appears to be a pair of large outer rings with a smaller central one, but the fine details cannot be seen. According to one theory for the formation of planetary nebulae, the hourglass shape is produced by the expansion of a fast stellar wind within a slowly expanding cloud which is more dense near its equator than near its poles. What appears as a bright elliptical ring in the center, and at first sight might be mistaken for an equatorially dense region, is seen on closer inspection to be a potato shaped structure with a symmetry axis dramatically different from that of the larger hourglass. The hot star which has been thought to eject and illuminate the nebula, and therefore expected to lie at its center of symmetry, is clearly off center. Hence MyCn18, as revealed by Hubble, does not fulfill some crucial theoretical expectations. Hubble has also revealed other features in MyCn18 which are completely new and unexpected. For example, there is a pair of intersecting elliptical rings in the central region which appear to be the rims of a smaller hourglass. There are the intricate patterns of the etchings on the hourglass walls. The arc-like etchings could be the remnants of discrete shells ejected from the star when it was younger (e.g. as seen in the Egg Nebula), flow instabilities, or could result from the action of a narrow beam of matter impinging on the hourglass walls. An unseen companion star and accompanying gravitational effects may well be necessary in order to explain the structure of MyCn18. BACKGROUND: PLANETARY NEBULAE When Sun-like stars get old, they become cooler and redder, increasing their sizes and energy output tremendously: they are called red giants. Most of the carbon (the basis of life) and particulate matter (crucial building blocks of solar systems like ours) in the universe is manufactured and dispersed by red giant stars. When the red giant star has ejected all of its outer layers, the ultraviolet radiation from the exposed hot stellar core makes the surrounding cloud of matter created during the red giant phase glow: the object becomes a planetary nebula. A long-standing puzzle is how planetary nebulae acquire their complex shapes and symmetries, since red giants and the gas/dust clouds surrounding them are mostly round. Hubble's ability to see very fine structural details (usually blurred beyond recognition in ground-based images) enables us to look for clues to this puzzle. Credits: Raghvendra Sahai and John Trauger (JPL), the WFPC2 science team, and NASA

Hubble Probes the Great Orion Nebula A NASA Hubble Space Telescope image of a region of the Great Nebula in Orion. This is one of the nearest regions of very recent star formation (300,000 years ago). The nebula is a giant gas cloud illuminated by the brightest of the young hot stars at the top of the picture. Many of the fainter young stars are surrounded by disks of dust and gas that are slightly more than twice the diameter of the Solar System. The great plume of gas in the lower left in this picture is the result of the ejection of material from a recently formed star. The brightest portions are "hills" on the surface of the nebula, and the long bright bar is where Earth observers look along a long "wall" on a gaseous surface. The diagonal length of the image is 1.6 light-years. Red light depicts emission in Nitrogen; green is Hydrogen; and blue is Oxygen. The Orion Nebula star-birth region is 1,500 light-years away, in the direction of the constellation Orion the Hunter. The image was taken on 29 December 1993 with the HST's Wide Field and Planetary Camera 2. Credit: C.R. O'Dell/Rice University; NASA

Hubble Finds a Young Planetary Nebula This is a NASA Hubble Space Telescope picture of a recently-formed "planetary nebula," known as Hen 1357. This expanding cloud of gas was ejected from the aging star in the center. Much of the gas is concentrated in a ring which appears tilted 35 degrees. This research is being presented at the 181st Meeting of the American Astronomical Society meeting in Phoenix, AZ on January 5, 1993. by Dr. Matt Bobrowsky of CTA INCORPORATED, in Rockville, Maryland. Besides the big clumps in the ring, HST's detailed images reveal many smaller clumps and wisps of gas, indicating turbulent motions and other activity in the nebula. Two bubbles of gas seen above and below the ring have burst open at their ends, allowing gas from inside to escape. Previous ground-based spectroscopic observations show that, over the past few decades, Hen 1357 changed from looking like an ordinary hot star to an obiect with the characteristics of a young planetary nebula. Although the central star may have begun to expel gas as much as a few thousand years ago, only recently has there been enough radiation from the star to make the gas glow. Before the Hubble observations, little was known about the nebula's structure because it is too small for anv detail to be seen using ground-based telescopes. Hen 1357 is about 18,000 light-years away and located in the southern constellation Ara the Altar. (The nebulae is so named because it is the 1357th object in a list of unusual stars compiled by astronomer Karl Henize.) The term "planetary nebula" is a misnomer because these objects have nothing to do with planets - aside from vaguely resembling the extended disk of a planet. Planetary nebulae form when an aging star swells to become a "red giant" and it then blows off some of its outer atmosphere. As the nebula expands, the remaining core of the star gets hotter and heats the gas until it glows with the characteristic colors of a planetary nebula. A fast "wind" from the star compresses the gas and pushes the gas bubble outward. A ring-like structure forms if more gas is lost from the star's equator than its poles. Hen 1357 is one of many young planetary nebulae which Bobrowsky is observing with HST. These observations will help astronomers understand how planetary nebula evolve in their early stages. Technical Information: This color photograph is 5 composite of separate images taken at wavelengths of light emitted by two chemical elements in the nebula. The green and yellow light is emitted by oxygen and the red light by hydrogen. The images were made with HST's Wide Field/Planetary Camera (in Planetary Camera mode) during several days in August 1992. Credit: Matt Bobrowsky (CTA INCORPORATED), and NASA.

SUPERNOVA SHOCK WAVE PAINTS COSMIC PORTRAIT Remnants from a star that exploded thousands of years ago created a celestial abstract portrait, as captured in this NASA Hubble Space Telescope image of the Pencil Nebula. Officially known as NGC 2736, the Pencil Nebula is part of the huge Vela supernova remnant, located in the southern constellation Vela. Discovered by Sir John Herschel in the 1840s, the nebula's linear appearance triggered its popular name. The nebula's shape suggests that it is part of the supernova shock wave that recently encountered a region of dense gas. It is this interaction that causes the nebula to glow, appearing like a rippled sheet. In this snapshot, astronomers are looking along the edge of the undulating sheet of gas. This view shows large, wispy filamentary structures, smaller bright knots of gas, and patches of diffuse gas. The Hubble Heritage Team used the Advanced Camera for Surveys in October 2002 to observe the nebula. The region of the Pencil Nebula captured in this image is about three-fourths of a light-year across. The Vela supernova remnant is 114 light-years (35 parsecs) across. The remnant is about 815 light-years (250 parsecs) away from our solar system. The nebula's luminous appearance comes from dense gas regions that have been struck by the supernova shock wave. As the shock wave travels through space [from right to left in the image], it rams into interstellar material. Initially the gas is heated to millions of degrees, but then subsequently cools down, emitting the optical light visible in the image. The colors of the various regions in the nebula yield clues about this cooling process. Some regions are still so hot that the emission is dominated by ionized oxygen atoms, which glow blue in the picture. Other regions have cooled more and are seen emitting red in the image (cooler hydrogen atoms). In this situation, color shows the temperature of the gas. The nebula is visible in this image because it is glowing. The supernova explosion left a spinning pulsar at the core of the Vela region. Based on the rate at which the pulsar is slowing down, astronomers estimate that the explosion may have occurred about 11,000 years ago. Although no historical records of the blast exist, the Vela supernova would have been 250 times brighter than Venus and would have been easily visible to southern observers in broad daylight. The age of the blast, if correct, would imply that the initial explosion pushed material from the star at nearly 22 million miles per hour. As the Vela supernova remnant expands, the speed of its moving filaments, such as the Pencil Nebula, decreases. The Pencil Nebula, for example, is moving at roughly 400,000 miles per hour. Image Credit: NASA and The Hubble Heritage Team (STScI/AURA) Acknowledgment: W. Blair (JHU) and D. Malin (David Malin Images)

Embryonic Stars Emerge from Interstellar "Eggs" Eerie, dramatic new pictures from NASA's Hubble Space Telescope show newborn stars emerging from "eggs" — not the barnyard variety — but rather dense, compact pockets of interstellar gas called evaporating gaseous globules (EGGs). Hubble found the "EGGs," appropriately enough, in the Eagle nebula, a nearby star-forming region 6,500 light- years away in the constellation Serpens.  "For a long time astronomers have speculated about what processes control the sizes of stars — about why stars are the sizes that they are," said Jeff Hester of Arizona State University, Tempe, AZ. "Now in M16 we seem to be watching at least one such process at work right in front of our eyes."  Striking pictures taken by Hester and co-investigators with Hubble's Wide Field and Planetary Camera 2 (WFPC2) resolve the EGGs at the tip of finger-like features protruding from monstrous columns of cold gas and dust in the Eagle nebula (also called M16 — 16th object in the Messier catalog). The columns — dubbed "elephant trunks" — protrude from the wall of a vast cloud of molecular hydrogen, like stalagmites rising above the floor of a cavern. Inside the gaseous towers, which are light-years long, the interstellar gas is dense enough to collapse under its own weight, forming young stars that continue to grow as they accumulate more and more mass from their surroundings.  Hubble gives a clear look at what happens as a torrent of ultraviolet light from nearby young, hot stars heats the gas along the surface of the pillars, "boiling it away" into interstellar space — a process called "photoevaporation. "The Hubble pictures show photoevaporating gas as ghostly streamers flowing away from the columns. But not all of the gas boils off at the same rate. The EGGs, which are denser than their surroundings, are left behind after the gas around them is gone.  "It's a bit like a wind storm in the desert," said Hester. "As the wind blows away the lighter sand, heavier rocks buried in the sand are uncovered. But in M16, instead of rocks, the ultraviolet light is uncovering the denser egg-like globules of gas that surround stars that were forming inside the gigantic gas columns."  Some EGGs appear as nothing but tiny bumps on the surface of the columns. Others have been uncovered more completely, and now resemble "fingers" of gas protruding from the larger cloud. (The fingers are gas that has been protected from photoevaporation by the shadows of the EGGs). Some EGGs have pinched off completely from the larger column from which they emerged, and now look like teardrops in space.  By stringing together these pictures of EGGs caught at different stages of being uncovered, Hester and his colleagues from the Wide Field and Planetary Camera Investigation Definition Team are getting an unprecedented look at what stars and their surroundings look like before they are truly stars.  "This is the first time that we have actually seen the process of forming stars being uncovered by photoevaporation," Hester emphasized. "In some ways it seems more like archaeology than astronomy. The ultraviolet light from nearby stars does the digging for us, and we study what is unearthed."  "In a few cases we can see the stars in the EGGs directly in the WFPC2 images," says Hester. "As soon as the star in an EGG is exposed, the object looks something like an ice cream cone, with a newly uncovered star playing the role of the cherry on top."  Ultimately, photoevaporation inhibits the further growth of the embyronic stars by dispersing the cloud of gas they were "feeding" from. "We believe that the stars in M16 were continuing to grow as more and more gas fell onto them, right up until the moment that they were cut off from that surrounding material by photoevaporation," said Hester.  This process is markedly different from the process that governs the sizes of stars forming in isolation. Some astronomers believe that, left to its own devices, a star will continue to grow until it nears the point where nuclear fusion begins in its interior. When this happens, the star begins to blow a strong "wind" that clears away the residual material. Hubble has imaged this process in detail in so-called Herbig-Haro objects.  Hester also speculated that photoevaporation might actually inhibit the formation of planets around such stars. It is not at all clear from the new data that the stars in M16 have reached the point where they have formed the disks that go on to become solar systems," said Hester, "and if these disks haven't formed yet, they never will."  Hester plans to use Hubble's high resolution to probe other nearby star-forming regions to look for similar structures. "Discoveries about the nature of the M16 EGGs might lead astronomers to rethink some of their ideas about the environments of stars forming in other regions, such as the Orion Nebula," he predicted.

Iridescent Glory of Nearby Planetary Nebula This photograph of the coil-shaped Helix Nebula is one of the largest and most detailed celestial images ever made. The composite picture is a seamless blend of ultra-sharp images from NASA's Hubble Space Telescope combined with the wide view of the Mosaic Camera on the National Science Foundation's 0.9-meter telescope at Kitt Peak National Observatory near Tucson, Ariz. The image shows a fine web of filamentary "bicycle-spoke" features embedded in the colorful red and blue ring of gas. At 650 light-years away, the Helix is one of the nearest planetary nebulae to Earth. A planetary nebula is the glowing gas around a dying, Sun-like star. Credit: NASA, NOAO, ESA, the Hubble Helix Nebula Team, M. Meixner (STScI), and T.A. Rector (NRAO).

Hubble Captures a Perfect Storm of Turbulent Gases Resembling the fury of a raging sea, this image actually shows a bubbly ocean of glowing hydrogen gas and small amounts of other elements such as oxygen and sulfur. The photograph, taken by NASA's Hubble Space Telescope, captures a small region within M17, a hotbed of star formation. M17, also known as the Omega or Swan Nebula, is located about 5,500 light-years away in the constellation Sagittarius. The image is being released to commemorate the thirteenth anniversary of Hubble's launch on April 24, 1990. The wave-like patterns of gas have been sculpted and illuminated by a torrent of ultraviolet radiation from young, massive stars, which lie outside the picture to the upper left. The glow of these patterns accentuates the three-dimensional structure of the gases. The ultraviolet radiation is carving and heating the surfaces of cold hydrogen gas clouds. The warmed surfaces glow orange and red in this photograph. The intense heat and pressure cause some material to stream away from those surfaces, creating the glowing veil of even hotter greenish gas that masks background structures. The pressure on the tips of the waves may trigger new star formation within them. The image, roughly 3 light-years across, was taken May 29-30, 1999, with the Wide Field Planetary Camera 2. The colors in the image represent various gases. Red represents sulfur; green, hydrogen; and blue, oxygen. Credit: NASA, ESA and J. Hester (ASU)

RAINBOW IMAGE OF A DUSTY STAR Resembling a rippling pool illuminated by underwater lights, the Egg Nebula offers astronomers a special look at the normally invisible dust shells swaddling an aging star. These dust layers, extending over one-tenth of a light-year from the star, have an onionskin structure that forms concentric rings around the star. A thicker dust belt, running almost vertically through the image, blocks off light from the central star. Twin beams of light radiate from the hidden star and illuminate the pitch-black dust, like a shining flashlight in a smoky room.  The artificial "Easter-Egg" colors in this image are used to dissect how the light reflects off the smoke-sized dust particles and then heads toward Earth.  Dust in our atmosphere reflects sunlight such that only light waves vibrating in a certain orientation get reflected toward us. This is also true for reflections off water or roadways. Polarizing sunglasses take advantage of this effect to block out all reflections, except those that align to the polarizing filter material. It's a bit like sliding a sheet of paper under a door. The paper must be parallel to the floor to pass under the door. Hubble's Advanced Camera for Surveys has polarizing filters that accept light that vibrates at select angles. In this composite image, the light from one of the polarizing filters has been colored red and only admits light from about one-third of the nebula. Another polarizing filter accepts light reflected from a different swath of the nebula. This light is colored blue. Light from the final third of the nebula is from a third polarizing filter and is colored green. Some of the inner regions of the nebula appear whitish because the dust is thicker and the light is scattered many times in random directions before reaching us. (Likewise, polarizing sunglasses are less effective if the sky is very dusty).  By studying polarized light from the Egg Nebula, scientists can tell a lot about the physical properties of the material responsible for the scattering, as well as the precise location of the central (hidden) star. The fine dust is largely carbon, manufactured by nuclear fusion in the heart of the star and then ejected into space as the star sheds material. Such dust grains are essential ingredients for building dusty disks around future generations of young stars, and possibly in the formation of planets around those stars.  The Egg Nebula is located 3,000 light-years away in the constellation Cygnus. This image was taken with Hubble's Advanced Camera for Surveys in September and October 2002.  Credit: NASA and The Hubble Heritage Team (STScI/AURA) Acknowledgment: W. Sparks (STScI) and R. Sahai (JPL)

Hubble Watches Light from Mysterious Erupting Star Reverberate Through Space In January 2002, a dull star in an obscure constellation suddenly became 600,000 times more luminous than our Sun, temporarily making it the brightest star in our Milky Way galaxy.  The mysterious star has long since faded back to obscurity, but observations by NASA's Hubble Space Telescope of a phenomenon called a "light echo" have uncovered remarkable new features. These details promise to provide astronomers with a CAT-scan-like probe of the three-dimensional structure of shells of dust surrounding an aging star. The results appear tomorrow in the journal Nature.  "Like some past celebrities, this star had its 15 minutes of fame," says Anne Kinney, director of NASA's Astronomy and Physics program, Headquarters, Washington. "But its legacy continues as it unveils an eerie light show in space. Thankfully, NASA's Hubble has a front row seat to this unique event in our galaxy."  Light from a stellar explosion echoing off circumstellar dust in our Milky Way galaxy was last seen in 1936, long before Hubble was available to study the tidal wave of light and reveal the netherworld of dusty black interstellar space.  "As light from the outburst continues to reflect off the dust surrounding the star, we view continuously changing cross-sections of the dust envelope. Hubble's view is so sharp that we can do an 'astronomical cat-scan' of the space around the star," says the lead observer, astronomer Howard Bond of the Space Telescope Science Institute in Baltimore.  Bond and his team used the Hubble images to determine that the petulant star, called V838 Monocerotis (V838 Mon) is about 20,000 light-years from Earth. The star put out enough energy in a brief flash to illuminate surrounding dust, like a spelunker taking a flash picture of the walls of an undiscovered cavern. The star presumably ejected the illuminated dust shells in previous outbursts. Light from the latest outburst travels to the dust and then is reflected to Earth. Because of this indirect path, the light arrives at Earth months after light coming directly toward Earth from the star itself.  The outburst of V838 Mon was somewhat similar to that of a nova, a more common stellar outburst. A typical nova is a normal star that dumps hydrogen onto a compact white-dwarf companion star. The hydrogen piles up until it spontaneously explodes by nuclear fusion — like a titanic hydrogen bomb. This exposes a searing stellar core, which has a temperature of hundreds of thousands of degrees Fahrenheit.  By contrast, however, V838 Mon did not expel its outer layers. Instead, it grew enormously in size, with its surface temperature dropping to temperatures not much hotter than a light bulb. This behavior of ballooning to an immense size, but not losing its outer layers, is very unusual and completely unlike an ordinary nova explosion.  "We are having a hard time understanding this outburst, which has shown a behavior that is not predicted by present theories of nova outbursts," says Bond. "It may represent a rare combination of stellar properties that we have not seen before."  The star is so unique it may represent a transitory stage in a star's evolution that is rarely seen. The star has some similarities to highly unstable aging stars called eruptive variables, which suddenly and unpredictably increase in brightness.  The circular light-echo feature has now expanded to twice the angular size of Jupiter on the sky. Astronomers expect it to continue expanding as reflected light from farther out in the dust envelope finally arrives at Earth. Bond predicts that the echo will be observable for the rest of this decade.  The research team included investigators from the Space Telescope Institute in Baltimore; the Universities Space Research Association at the U.S. Naval Observatory in Flagstaff, Ariz.; the European Space Agency; Arizona State University; the Large Binocular Telescope Observatory at the University of Arizona at Tucson; the Isaac Newton Group of Telescopes in Spain's Canary Islands; and the INAF-Osservatorio Astronomico di Padova in Asiago, Italy.

 

Protoplanetary Disks Around Newly Formed Stars NASA's Hubble Space Telescope has uncovered the strongest evidence yet that many stars form planetary systems.  Dr. C. Robert O'Dell of Rice University, Houston, Texas and colleagues have used Hubble to discover extended disks of dust around 15 newly formed stars in the Orion Nebula, a star birth region 1,500 light-years away.  Such disks are a prerequisite for the formation of solar Systems like our own. "These images provide the best evidence for planetary systems," said O'Dell.  "The disks are a missing link in our understanding of how planets like those in our Solar System form. Their discovery establishes that the basic material of planets exists around a large fraction of stars. It is likely that many of these stars will have planetary systems."  Hubble Space Telescope's detailed images confirm more than a century of speculation, conjecture and theory about the genesis of a solar system.  According to current theories the dust contained within the disks eventually agglomerates to make planets. Our Solar System is considered a relic of just such a disk of dust that accompanied our Sun's birth 4.5 billion years ago.  Before the Hubble discovery, protoplanetary disks have been confirmed around only four stars: Beta Pictoris, Alpha Lyrae, Alpha Piscis Austrini, and Epsilon Eridani.  Unlike these previous observations, Hubble has observed newly formed stars less than a million years old which are still contracting out of primordial gas.  Hubble's images provide direct evidence that dust surrounding a newborn star has too much spin to be drawn into the collapsing star. Instead the material spreads out into a broad, flattened disk.  These young disks signify an entirely new class of object uncovered in the universe, according to O'Dell. (He calls them Proplyds following the suggestion of his wife, Gail Sabanosh, who noted that for him protoplanetary disks was too much of a tongue twister.)  Hubble can see the disks because they are illuminated by the hottest stars in the Orion Nebula, and some of them are seen in silhouette against the bright nebula. However, some of these proplyds are bright enough to have been seen previously by ground-based optical and radio telescopes as stars. Their true nature was not recognized until the Hubble discovery.  Each proplyd appears as thick disk with a hole in the middle where the cool star is located. Radiation from nearby hot stars "boils off" material from the disk's surface (at the rate of about one half the mass of our Earth per year). This material is then blown back into a comet-like tail by a stellar “wind” of radiation and subatomic particles streaming from nearby hot stars.  Based on this erosion rate, O'Dell estimates that a proplyd's initial mass would be at least 15 times that of the giant planet Jupiter.  Many of the youngest and hottest stars in our Milky Way Galaxy are found in the Orion Nebula. The nebula is on the near edge of a giant molecular cloud which lies immediately behind the stars which trace the sword of the constellation of Orion the Hunter. The region of Orion studied intensely by O'Dell and collaborators is a bright part Of the nebula where stars are being uncovered at the highest rate. These results suggest that nearly half the 50 stars in this part of Orion have protoplanetary disks.  O'Dell's co-investigators are graduate students Zheng Wen and Xi-Hai Hu of Rice University, and Dr. Jeff Hester of Arizona State University. Their results will be published in Astrophysical Journal next spring, title: "Discovery of New Objects in the Orion Nebula on HST Images: Shocks, Compact Sources, and Protoplanetary Disks."  Release Date: 12:00AM (EST) December 16, 1992

The Coldest Spot In The Universe Revealed in all it's glory in this Hubble Space Telescope image, the Boomerang Nebula registers in at a bone chilling -458F. That's 1° above absolute zero... the point at which atomic activity ceases. Find out more at CNN.com/SPACE.

Close-Up of M27, the Dumbbell Nebula An aging star's last hurrah is creating a flurry of glowing knots of gas that appear to be streaking through space in this close-up image of the Dumbbell Nebula, taken with NASA's Hubble Space Telescope.  The Dumbbell, a nearby planetary nebula residing more than 1,200 light-years away, is the result of an old star that has shed its outer layers in a glowing display of color. The nebula, also known as Messier 27 (M27), was the first planetary nebula ever discovered. French astronomer Charles Messier spotted it in 1764.  The Hubble images of the Dumbbell show many knots, but their shapes vary. Some look like fingers pointing at the central star, located just off the upper left of the image; others are isolated clouds, with or without tails. Their sizes typically range from 11 - 35 billion miles (17 - 56 billion kilometers), which is several times larger than the distance from the Sun to Pluto. Each contains as much mass as three Earths.  The knots are forming at the interface between the hot (ionized) and cool (neutral) portion of the nebula. This area of temperature differentiation moves outward from the central star as the nebula evolves. In the Dumbbell astronomers are seeing the knots soon after this hot gas passed by.  Dense knots of gas and dust seem to be a natural part of the evolution of planetary nebulae. They form in the early stages, and their shape changes as the nebula expands. Similar knots have been discovered in other nearby planetary nebulae that are all part of the same evolutionary scheme. They can be seen in Hubble telescope photos of the Ring Nebula (NGC 6720), the Eskimo Nebula (NGC 2392) and the Retina Nebula (IC 4406). The detection of these knots in all the nearby planetaries imaged by the Hubble telescope allows astronomers to hypothesize that knots may be a feature common in all planetary nebulae.  This image, created by the Hubble Heritage Team (STScI), was taken by Hubble's Wide Field Planetary Camera 2 in November 2001, by Bob O'Dell (Vanderbilt University) and collaborators. The filters used to create this color image show oxygen in blue, hydrogen in green and a combination of sulfur and nitrogen emission in red.  Image Credit: NASA and the Hubble Heritage Team (STScI/AURA) Acknowledgment: C.R. O'Dell (Vanderbilt University)

THE INTERPLAY OF STARLIGHT, GAS, AND DUST IN THE LARGE MAGELLANIC CLOUD Complex interactions of starlight with interstellar gas and dust in a nearby galaxy are revealed in a new image obtained by NASA's Hubble Space Telescope and presented by the Hubble Heritage team.  Hubble's Wide Field Planetary Camera 2 (WFPC2) was positioned on a small region within a gas cloud, or nebula, called DEM L 106. It belongs to the Large Magellanic Cloud, a galaxy lying 160,000 light-years from our own Milky Way galaxy. DEM L 106 appears in this image as the faint, glowing hydrogen gas that covers most of the picture. This nebula was originally cataloged in the 1970's by astronomers R. Davies, K. Elliot, and J. Meaburn, who created the "DEM" catalogs of both the Large and Small Magellanic Clouds.  The smaller and much brighter gas cloud near the top of the image, called N30B, was discovered in the 1950's by astronomer K. Henize, who later became a NASA astronaut. The N30B nebula surrounds a group of hot, blue stars that have recently formed through gravitational contraction of the gas. The ultraviolet radiation streaming out from these blue stars strips electrons off of the hydrogen atoms in the surrounding gas, causing the gas to glow through a process of fluorescence.  The very bright star near the upper left corner of the picture is cataloged as Henize S22; it is a very hot and luminous supergiant star, lying only 25 light-years from the N30B nebula. It is a rare and peculiar type of blue star that is believed to be surrounded by a dense, dusty disk. This disk reddens the light from the star, just as the dusty Earth atmosphere reddens sunlight at sunset. As viewed from N30B, S22 would appear some 250 times as bright as the planet Venus does in Earth's sky. This bright starlight illuminates interstellar dust particles in N30B, producing a faint glow around it, called a reflection nebula, that somewhat resembles the numeral 8 turned on its side. The band of gas across the bottom of the image is part of the shell wall of a giant superbubble created by the stellar wind of S22. The shroud of gas  surrounding N30B also shows a bow shock from the S22 wind.   Lowell Observatory astronomer M.S. Oey and University of Illinois astronomer Y.-H. Chu are members of a science team studying DEM L 106. Along with their collaborators, Oey and Chu have made a clever use of the reflection nebula around N30B. By obtaining spectroscopic observations at various points across the nebula, they can study the spectrum of S22 from different angles. Remarkably, they have found that the star's spectrum changes with viewing angle, confirming that the star is surrounded by a flattened disk of gas, that is probably expelled from its equator. (See supplemental page for more information.)  Archived Hubble images of DEM L 106 taken in 1998 were combined with data taken by the Hubble Heritage Team in late 2001. The final image shows emission in hydrogen and ionized sulfur, as well as stellar colors at blue, visual and infrared wavelengths.  Credits: NASA and The Hubble Heritage Team (STScI/AURA) Acknowledgment: M.S. Oey (Lowell Observatory) and Y.-H. Chu (U. of Illinois)

Star Birth in the Trifid Nebula This NASA Hubble Space Telescope image of the Trifid Nebula reveals a stellar nursery being torn apart by radiation from a nearby, massive star. The picture also provides a peek at embryonic stars that are forming within an ill-fated cloud of dust and gas that is destined to be eaten away by the glare from the massive neighbor. This stellar activity is a beautiful example of how the life cycle of stars like our Sun is intimately connected with their more powerful siblings.  The Hubble image shows a small part of a dense cloud of dust and gas, a stellar nursery full of embryonic stars. This cloud is about 8 light-years away from the nebula's central star, which is beyond the top of this picture. Located about 9,000 light-years from Earth, the Trifid resides in the constellation Sagittarius.  A stellar jet [the thin, wispy object pointing to the upper left] protrudes from the head of a dense cloud and extends three-quarters of a light-year into the nebula. The jet's source is a very young stellar object that lies buried within the cloud. Jets such as this are the exhaust gases of star formation. Radiation from the massive star at the center of the nebula is making the gas in the jet glow, just as it causes the rest of the nebula to glow.  The jet in the Trifid is a "ticker tape," telling the history of one particular young stellar object that is continuing to grow as its gravity draws in gas from its surroundings. But this particular ticker tape will not run for much longer. Within the next 10,000 years the glare of the central, massive star will continue to erode the nebula, overrunning the forming star, and bringing its growth to an abrupt and possibly premature end.  Another nearby star may have already faced this fate. The Hubble picture shows a "stalk" [the finger-like object] pointing from the head of the dense cloud directly toward the star that powers the Trifid. This stalk is a prominent example of the evaporating gaseous globules, or "EGGs," that were seen previously in the Eagle Nebula, another star-forming region photographed by Hubble. The stalk has survived because at its tip there is a knot of gas that is dense enough to resist being eaten away by the powerful radiation.  Reflected starlight at the tip of the EGG may be due to light from the Trifid's central star or from a young stellar object buried within the EGG. Similarly, a tiny spike of emission pointing outward from the EGG looks like a small stellar jet. Hubble astronomers are tentatively interpreting this jet as the last gasp from a star that was cut off from its supply lines 100,000 years ago.  The images were taken Sept. 8, 1997 through filters that isolate emission from hydrogen atoms, ionized sulfur atoms, and doubly ionized oxygen atoms. The images were combined in a single color composite picture. While the resulting picture is not true color, it is suggestive of what a human eye might see.  Credits: NASA and Jeff Hester (Arizona State University)

Hubble Photographs 'Double Bubble' in Neighboring Galaxy  A unique peanut-shaped cocoon of dust, called a reflection nebula, surrounds a cluster of young, hot stars in this view from NASA's Hubble Space Telescope. The "double bubble," called N30B, is inside a larger nebula. The larger nebula, called DEM L 106, is embedded in the Large Magellanic Cloud, a satellite galaxy of our Milky Way lying 160,000 light-years away. The wispy filaments of DEM L 106 fill much of the image. Hubble captures the glow of fluorescing hydrogen and sulfur, as well as the brilliant blue-white colors of the hot stars.  The very bright star at the top of the picture, called Henize S22, illuminates the dusty cocoon like a flashlight shining on smoke particles. This searing supergiant star is only 25 light-years from the N30B nebula. Viewed from N30B, the brilliant star would appear 250 times as bright as the planet Venus does in Earth's sky.  Lowell Observatory astronomer M.S. Oey and University of Illinois astronomer Y.-H. Chu are members of a science team studying DEM L 106. Along with their collaborators, Oey and Chu have made a clever use of the reflection nebula around N30B. By obtaining spectroscopic observations at various points across the nebula, they can study the spectrum of S22 from different angles. Remarkably, they have found that the star's spectrum changes with the viewing angle, suggesting that the star is surrounded by a flattened disk of gas expelled from its equator.  Astronomers R. Davies, K. Elliot, and J. Meaburn, who created the "DEM" catalogs of both the Large and Small Magellanic Clouds, originally cataloged DEM L 106 in the 1970's. N30B was discovered in the 1950s by astronomer K. Henize, who later became a NASA astronaut.  DEM L 106 was imaged with Hubble's Wide Field Planetary Camera 2 (WFPC2). Hubble data taken in 1998 were combined with data taken by the Hubble Heritage Team in late 2001.  Credit: NASA and The Hubble Heritage Team (STScI/AURA) Acknowledgment: M.S. Oey (Lowell Observatory) and Y.-H. Chu (U. of Illinois)

Looking Down a Barrel of Gas at a Doomed Star The NASA Hubble Space Telescope has captured the sharpest view yet of the most famous of all planetary nebulae: the Ring Nebula (M57). In this October 1998 image, the telescope has looked down a barrel of gas cast off by a dying star thousands of years ago. This photo reveals elongated dark clumps of material embedded in the gas at the edge of the nebula; the dying central star floating in a blue haze of hot gas. The nebula is about a light-year in diameter and is located some 2,000 light-years from Earth in the direction of the constellation Lyra. The colors are approximately true colors. The color image was assembled from three black-and-white photos taken through different color filters with the Hubble telescope's Wide Field Planetary Camera 2. Blue isolates emission from very hot helium, which is located primarily close to the hot central star. Green represents ionized oxygen, which is located farther from the star. Red shows ionized nitrogen, which is radiated from the coolest gas, located farthest from the star. The gradations of color illustrate how the gas glows because it is bathed in ultraviolet radiation from the remnant central star, whose surface temperature is a white-hot 216,000 degrees Fahrenheit (120,000 degrees Celsius). Credit: Hubble Heritage Team (AURA/STScI/NASA)

An Old Star Gives Up the Ghost NASA's Hubble Space Telescope has recently obtained images of the planetary nebula NGC 6369. This object is known to amateur astronomers as the "Little Ghost Nebula," because it appears as a small, ghostly cloud surrounding the faint, dying central star. NGC 6369 lies in the direction of the constellation Ophiuchus, at a distance estimated to be between about 2,000 and 5,000 light-years from Earth.  When a star with a mass similar to that of our own Sun nears the end of its lifetime, it expands in size to become a red giant. The red-giant stage ends when the star expels its outer layers into space, producing a faintly glowing nebula. Astronomers call such an object a planetary nebula, because its round shape resembles that of a planet when viewed with a small telescope.  The Hubble photograph of NGC 6369, captured with the Wide Field Planetary Camera 2 (WFPC2) in February 2002, reveals remarkable details of the ejection process that are not visible from ground-based telescopes because of the blurring produced by the Earth's atmosphere.  The remnant stellar core in the center is now sending out a flood of ultraviolet (UV) light into the surrounding gas. The prominent blue-green ring, nearly a light-year in diameter, marks the location where the energetic UV light has stripped electrons off of atoms in the gas. This process is called ionization. In the redder gas at larger distances from the star, where the UV light is less intense, the ionization process is less advanced. Even farther outside the main body of the nebula, one can see fainter wisps of gas that were lost from the star at the beginning of the ejection process.  The color image has been produced by combining WFPC2 pictures taken through filters that isolate light emitted by three different chemical elements with different degrees of ionization. The doughnut-shaped blue-green ring represents light from ionized oxygen atoms that have lost two electrons (blue) and from hydrogen atoms that have lost their single electrons (green). Red marks emission from nitrogen atoms that have lost only one electron.  Our own Sun may eject a similar nebula, but not for another 5 billion years. The gas will expand away from the star at about 15 miles per second, dissipating into interstellar space after some 10,000 years. After that, the remnant stellar ember in the center will gradually cool off for billions of years as a tiny white dwarf star, and eventually wink out.  Credit: NASA and The Hubble Heritage Team (STScI/AURA)

Beauty in the Eye of Hubble  A dying star, IC 4406, dubbed the "Retina Nebula" is revealed in this month's Hubble Heritage image.  Like many other so-called planetary nebulae, IC 4406 exhibits a high degree of symmetry; the left and right halves of the Hubble image are nearly mirror images of the other. If we could fly around IC4406 in a starship, we would see that the gas and dust form a vast donut of material streaming outward from the dying star. From Earth, we are viewing the donut from the side. This side view allows us to see the intricate tendrils of dust that have been compared to the eye's retina. In other planetary nebulae, like the Ring Nebula (NGC 6720), we view the donut from the top.  The donut of material confines the intense radiation coming from the remnant of the dying star. Gas on the inside of the donut is ionized by light from the central star and glows. Light from oxygen atoms is rendered blue in this image; hydrogen is shown as green, and nitrogen as red. The range of color in the final image shows the differences in concentration of these three gases in the nebula.   Unseen in the Hubble image is a larger zone of neutral gas that is not emitting visible light, but which can be seen by radio telescopes.   One of the most interesting features of IC 4406 is the irregular lattice of dark lanes that criss-cross the center of the nebula. These lanes are about 160 astronomical units wide (1 astronomical unit is the distance between the Earth and Sun). They are located right at the boundary between the hot glowing gas that produces the visual light imaged here and the neutral gas seen with radio telescopes. We see the lanes in silhouette because they have a density of dust and gas that is a thousand times higher than the rest of the nebula. The dust lanes are like a rather open mesh veil that has been wrapped around the bright donut. The fate of these dense knots of material is unknown. Will they survive the nebula's expansion and become dark denizens of the space between the stars or simply dissipate?  This image is a composite of data taken by Hubble's Wide Field Planetary Camera 2 in June 2001 by Bob O'Dell (Vanderbilt University) and collaborators and in January 2002 by The Hubble Heritage Team (STScI). Filters used to create this color image show oxygen, hydrogen, and nitrogen gas glowing in this object.  Image Credit: NASA and The Hubble Heritage Team (STScI/AURA) Acknowledgment: C.R. O'Dell (Vanderbilt University)

NICMOS Peels Away Layers of Dust to Show Inner Region of Dusty Nebula The revived Near Infrared Camera and Multi-Object Spectrometer (NICMOS) aboard NASA's Hubble Space Telescope has penetrated layers of dust in a star-forming cloud to uncover a dense, craggy edifice of dust and gas [image at right].   This region is called the Cone Nebula (NGC 2264), so named because, in ground-based images, it has a conical shape. NICMOS enables the Hubble telescope to see in near-infrared wavelengths of light, so that it can penetrate the dust that obscures the nebula's inner regions. But the Cone is so dense that even the "near-infared eyes" of NICMOS can't penetrate all the way through it.  The image shows the tip of the nebula, about half a light-year long. The entire nebula is 7 light-years long. The Cone resides in a turbulent star-forming region, located 2,500 light-years away in the constellation Monoceros.  Radiation from hot, young stars [located beyond the top of the image] has slowly eroded the nebula over millions of years. Ultraviolet light heats the edges of the dark cloud, releasing gas into the relatively empty region of surrounding space.   NICMOS has peeled away the outer layers of dust to reveal even denser dust. The denser regions give the nebula a more three-dimensional structure than can be seen in the visible-light picture at left, taken by the Advanced Camera for Surveys aboard the Hubble telescope. In peering through the dusty façade to the nebula's inner regions, NICMOS has unmasked several stars [yellow dots at upper right]. Astronomers don't know whether these stars are behind the dusty nebula or embedded in it. The four bright stars lined up on the left are in front of the nebula.   The human eye cannot see infrared light, so colors have been assigned to correspond with near-infrared wavelengths. The blue light represents shorter near-infrared wavelengths and the red light corresponds to longer wavelengths.   The NICMOS color composite image was made by combining photographs taken in J-band, H-band, and Paschen-alpha filters. The NICMOS images were taken on May 11, 2002.  Credits for NICMOS image: NASA, the NICMOS Group (STScI, ESA), and the NICMOS Science Team (University of Arizona)   Credits for ACS image: NASA, H. Ford (JHU), G. Illingworth (UCSC/LO), M.Clampin (STScI), G. Hartig (STScI), the ACS Science Team, and ESA

Gaseous Streamers Flutter in Stellar Breeze Resembling the hair in Botticelli's famous portrait of the birth of Venus, softly glowing filaments stream from a complex of hot young stars. This image of a nebula, known as N44C, comes from the archives of NASA's Hubble Space Telescope (HST). It was taken with the Wide Field Planetary Camera 2 in 1996 and is being presented by the Hubble Heritage Project.  N44C is the designation for a region of glowing hydrogen gas surrounding an association of young stars in the Large Magellanic Cloud, a nearby, small companion galaxy to the Milky Way visible from the Southern Hemisphere.   N44C is peculiar because the star mainly responsible for illuminating the nebula is unusually hot. The most massive stars, ranging from 10-50 times more massive than the Sun, have maximum temperatures of 54,000 to 90,000 degrees Fahrenheit (30,000 to 50,000 degrees Kelvin). The star illuminating N44C appears to be significantly hotter, with a temperature of about 135,000 degrees Fahrenheit (75,000 degrees Kelvin)!   Ideas proposed to explain this unusually high temperature include the possibility of a neutron star or black hole that intermittently produces X-rays but is now "switched off."  On the top right of this Hubble image is a network of nebulous filaments that inspired comparison to Botticelli. The filaments surround a Wolf-Rayet star, another kind of rare star characterized by an exceptionally vigorous "wind" of charged particles. The shock of the wind colliding with the surrounding gas causes the gas to glow.   N44C is part of the larger N44 complex, which includes young, hot, massive stars, nebulae, and a "superbubble" blown out by multiple supernova explosions. Part of the superbubble is seen in red at the very bottom left of the HST image.   The data were taken in November 1996 with Hubble's Wide Field Planetary Camera 2 by Donald Garnett (University of Arizona) and collaborators and stored in the Hubble archive. The image was composed by the Hubble Heritage Team (STScI/AURA). Image Credit: NASA and The Hubble Heritage Team (STScI/AURA) Acknowledgment: D. Garnett (University of Arizona)

Hubble's Newest Camera Eyes Hotbed of Star Formation A watercolor fantasyland? No. It's actually an image of the center of the Omega Nebula, a hotbed of newly born stars wrapped in colorful blankets of glowing gas and cradled in an enormous cold, dark hydrogen cloud. This stunning picture was taken by the newly installed Advanced Camera for Surveys (ACS) aboard NASA's Hubble Space Telescope.   The region of the nebula shown in this photograph is about 3,500 times wider than our solar system. The area represents about 60 percent of the total view captured by ACS. The nebula, also called M17 and the Swan Nebula, resides 5,500 light-years away in the constellation Sagittarius.   Like its famous cousin in Orion, the Swan Nebula is illuminated by ultraviolet radiation from young, massive stars, located just beyond the upper right corner of the image. Each star is about six times hotter and 30 times more massive than the Sun. The powerful radiation from these stars evaporates and erodes the dense cloud of cold gas within which the stars formed. The blistered walls of the hollow cloud shine primarily in the blue, green, and red light emitted by excited atoms of hydrogen, nitrogen, oxygen, and sulfur. Particularly striking is the rose-like feature, seen to the right of center, which glows in the red light emitted by hydrogen and sulfur.   As the infant stars evaporate the surrounding cloud, they expose dense pockets of gas that may contain developing stars. Because these dense pockets are more resistant to the withering radiation than the surrounding cloud, they appear as sculptures in the walls of the cloud or as isolated islands in a sea of glowing gas. One isolated pocket is seen at the center of the brightest region of the nebula and is about 10 times larger than our solar system. Other dense pockets of gas have formed the remarkable feature jutting inward from the left edge of the image, which resembles the famous Horsehead Nebula in Orion.   ACS made this observation on April 1 and 2, 2002. The color image is constructed from four separate images taken in these filters: blue, near infrared, hydrogen alpha, and doubly ionized oxygen.   Credit: NASA, H. Ford (JHU), G. Illingworth (USCS/LO), M.Clampin  (STScI), G. Hartig (STScI), the ACS Science Team, and ESA

Hubble's Newest Camera Images Monstrous Star-Forming Pillar of Gas and Dust Resembling a nightmarish beast rearing its head from a crimson sea, this monstrous object is actually an innocuous pillar of gas and dust. Called the Cone Nebula (NGC 2264) — so named because, in ground-based images, it has a conical shape — this giant pillar resides in a turbulent star-forming region.   This picture, taken by the newly installed Advanced Camera for Surveys (ACS) aboard NASA's Hubble Space Telescope, shows the upper 2.5 light-years of the nebula, a height that equals 23 million roundtrips to the Moon. The entire nebula is 7 light-years long. The Cone Nebula resides 2,500 light-years away in the constellation Monoceros.   Radiation from hot, young stars [located beyond the top of the image] has slowly eroded the nebula over millions of years. Ultraviolet light heats the edges of the dark cloud, releasing gas into the relatively empty region of surrounding space. There, additional ultraviolet radiation causes the hydrogen gas to glow, which produces the red halo of light seen around the pillar. A similar process occurs on a much smaller scale to gas surrounding a single star, forming the bow-shaped arc seen near the upper left side of the Cone. This arc, seen previously with the Hubble telescope, is 65 times larger than the diameter of our solar system. The blue-white light from surrounding stars is reflected by dust. Background stars can be seen peeking through the evaporating tendrils of gas, while the turbulent base is pockmarked with stars reddened by dust.   Over time, only the densest regions of the Cone will be left. Inside these regions, stars and planets may form.   The Cone Nebula is a cousin of the M16 pillars, which the Hubble telescope imaged in 1995. Monstrous pillars of cold gas, like the Cone and M16, are common in large regions of star birth. Astronomers believe that these pillars are incubators for developing stars.   ACS made this observation on April 2, 2002.  The color image is constructed from three separate images taken in blue, near-infrared, and hydrogen-alpha filters.   Credit: NASA and the ACS Science Team

Hubble's Panoramic Portrait of a Vast Star-Forming Region  NASA's Hubble Space Telescope has snapped a panoramic portrait of a vast, sculpted landscape of gas and dust where thousands of stars are being born. This fertile star-forming region, called the 30 Doradus Nebula, has a sparkling stellar centerpiece: the most spectacular cluster of massive stars in our cosmic neighborhood of about 25 galaxies.   The mosaic picture shows that ultraviolet radiation and high-speed material  unleashed by the stars in the cluster, called R136 [the large blue blob left of center], are weaving a tapestry of creation and destruction, triggering the collapse of looming gas and dust clouds and forming pillar-like structures that are incubators for nascent stars.   The photo offers an unprecedented, detailed view of the entire inner region of 30 Doradus, measuring 200 light-years wide by 150 light-years high. The nebula resides in the Large Magellanic Cloud (a satellite galaxy of the Milky Way), 170,000 light-years from Earth.  Nebulas like 30 Doradus are the "signposts" of recent star birth. High-energy ultraviolet radiation from the young, hot, massive stars in R136 causes the surrounding gaseous material to glow. Previous Hubble telescope observations showed that R136 contains several dozen of the most massive stars known, each about 100 times the mass of the Sun and about 10 times as hot. These stellar behemoths all formed at the same time about 2 million years ago.  The stars in R136 are producing intense "stellar winds" (streams of material traveling at several million miles an hour), which are wreaking havoc on the gas and dust in the surrounding neighborhood. The winds are pushing the gas away from the cluster and compressing the inner regions of the surrounding gas and dust clouds [the pinkish material]. The intense pressure is triggering the collapse of parts of the clouds, producing a new generation of star formation around the central cluster. The new stellar nursery is about 30 to 50 light-years from R136. Most of the stars in the nursery are not visible because they are still encased in their cocoons of gas and dust.  Some of the nascent stars are forming in long columns of gas and dust. Previous Hubble observations revealed that the process of "triggered" star formation often involves massive pillars of material that point toward the central cluster. Such pillars form when particularly dense clouds of gas and dust shield columns of material behind them from the blistering radiation and strong winds released by massive stars, like the stars in R136. This protected material becomes the pillars where stars can form and grow. The Hubble telescope first spied these pillars of stellar creation when it captured close-up views of the Eagle Nebula.  The new image of 30 Doradus shows numerous pillars — each several light-years long — oriented toward the central cluster. These pillars, which resemble tiny fingers, are similar in size to those in the Eagle Nebula. Without Hubble's resolution, they would not be visible. One pillar is visible within the oval-shaped structure to the left of the cluster. Two [one dark and one bright] are next to each other below and to the right of the cluster. One pillar is at upper right, and still another is just above the cluster.   Newborn stars within most of these pillars already have been discovered in pictures taken by Hubble's infrared camera, the Near Infrared Camera and Multi-Object Spectrometer, which can penetrate the dust to detect embryonic stars. Eventually, intense radiation and stellar winds from the developing stars will blow off the tops of the pillars. The Hubble image shows that one such eruption already has occurred in 30 Doradus. A trio of young stars has just been "born" by breaking out of its natal pillar. These new stars are just a few hundred thousand years old.  In another 2 million years, the new generation of stars will be in full bloom. But the massive stars in R136 will have burned themselves out. And the nebula's central region will be a giant shell, devoid of gas and dust. Still later, all of the most massive stars and gas will have disappeared from the entire region. Only older, less massive stars will remain in a region cleared of gas and dust.  The mosaic image of 30 Doradus consists of five overlapping pictures taken between January 1994 and September 2000 by Hubble's Wide Field and Planetary Camera 2. Several color filters were used to enhance important details in the stars and the nebula. Blue corresponds to the hot stars. The greenish color denotes hot gas energized by the central cluster of stars. Pink depicts the glowing edges of the gas and dust clouds facing the cluster, which are being bombarded by winds and radiation. Reddish-brown represents the cooler surfaces of the clouds, which are not receiving direct radiation from the central cluster.  Credits: NASA, N. Walborn and J. Maíz-Apellániz (Space Telescope Science Institute, Baltimore, MD), R. Barbá (La Plata Observatory, La Plata, Argentina)

A BOW SHOCK NEAR A YOUNG STAR NASA's Hubble Space Telescope continues to reveal various stunning and intricate treasures that reside within the nearby, intense star-forming region known as the Great Nebula in Orion. One such jewel is the bow shock around the very young star, LL Ori, featured in this Hubble Heritage image.  Named for the crescent-shaped wave made by a ship as it moves through water, a bow shock can be created in space when two streams of gas collide. LL Ori emits a vigorous solar wind, a stream of charged particles moving rapidly outward from the star. Our own Sun has a less energetic version of this wind that is responsible for auroral displays on the Earth.   The material in the fast wind from LL Ori collides with slow-moving gas evaporating away from the center of the Orion Nebula, which is located to the lower right in this Heritage image. The surface where the two winds collide is the crescent-shaped bow shock seen in the image.   Unlike a water wave made by a ship, this interstellar bow shock is a three-dimensional structure. The filamentary emission has a very distinct boundary on the side facing away from LL Ori, but is diffuse on the side closest to the star, a characteristic common to many bow shocks.   A second, fainter bow shock can be seen around a star near the upper right-hand corner of the Heritage image. Astronomers have identified numerous shock fronts in this complex star-forming region and are using this data to understand the many complex phenomena associated with the birth of stars.  This image was taken in February 1995 as part of the Hubble Orion Nebula mosaic. A nearby neighbor in our Milky Way galaxy, the nebula is only 1,500 light-years from Earth. The filters used in this color composite represent oxygen, nitrogen, and hydrogen emissions.  Image Credit: NASA and the Hubble Heritage Team (STScI/AURA) Acknowledgment: C. R. O'Dell (Vanderbilt University)

LIGHT AND SHADOW IN THE CARINA NEBULA  Previously unseen details of a mysterious, complex structure within the Carina Nebula (NGC 3372) are revealed by this image of the "Keyhole Nebula," obtained with NASA's Hubble Space Telescope. The picture is a montage assembled from four different April 1999 telescope pointings with Hubble's Wide Field Planetary Camera 2, which used six different color filters.   The picture is dominated by a large, approximately circular feature, which is part of the Keyhole Nebula, named in the 19th century by Sir John Herschel. This region, about 8000 light-years from Earth, is located adjacent to the famous explosive variable star Eta Carinae, which lies just outside the field of view toward the upper right. The Carina Nebula also contains several other stars that are among the hottest and most massive known, each about 10 times as hot, and 100 times as massive, as our Sun.   The circular Keyhole structure contains both bright filaments of hot, fluorescing gas, and dark silhouetted clouds of cold molecules and dust, all of which are in rapid, chaotic motion. The high resolution of the Hubble images reveals the relative three-dimensional locations of many of these features, as well as showing numerous small dark globules that may be in the process of collapsing to form new stars.   Two striking large, sharp-edged dust clouds are located near the bottom center and upper left edges of the image. The former is immersed within the ring and the latter is just outside the ring. The pronounced pillars and knobs of the upper left cloud appear to point toward a luminous, massive star located just outside the field further toward the upper left, which may be responsible for illuminating and sculpting them by means of its high-energy radiation and stellar wind of high-velocity ejected material. These large dark clouds may eventually evaporate, or if there are sufficiently dense condensations within them, give birth to small star clusters.   The Carina Nebula, with an overall diameter of more than 200 light-years, is one of the outstanding features of the Southern-Hemisphere portion of the Milky Way. The diameter of the Keyhole ring structure shown here is about 7 light-years.   These data were collected by the Hubble Heritage Team and Nolan R. Walborn (STScI), Rodolfo H. Barbá (La Plata Observatory, Argentina), and Adeline Caulet (France).   Image Credit: NASA and The Hubble Heritage Team (AURA/STScI)  Acknowledgment: N. Walborn (STScI) and R. Barbá (La Plata Observatory, Argentina)

Hubble Peeks into a Stellar Nursery in a Nearby Galaxy NASA's Hubble Space Telescope has peered deep into a neighboring galaxy to reveal details of the formation of new stars. Hubble's target was a newborn star cluster within the Small Magellanic Cloud, a small galaxy that is a satellite of our own Milky Way. The new images show young, brilliant stars cradled within a nebula, or glowing cloud of gas, cataloged as N 81.   These massive, recently formed stars inside N 81 are losing material at a high rate, sending out strong stellar winds and shock waves and hollowing out a cocoon within the surrounding nebula. The two most luminous stars, seen in the Hubble image as a very close pair near the center of N 81, emit copious ultraviolet radiation, causing the nebula to glow through fluorescence.   Outside the hot, glowing gas is cooler material consisting of hydrogen molecules and dust. Normally this material is invisible, but some of it can be seen in silhouette against the nebular background,as long dust lanes and a small, dark, elliptical-shaped knot. It is believed that the young stars have formed from this cold matter through gravitational contraction.   Few features can be seen in N 81 from ground-based telescopes, earning it the informal nick-name "The Blob." Astronomers were not sure if just one or a few hot stars were embedded in the cloud, or if it was a stellar nursery containing a large number of less massive stars. Hubble's high-resolution imaging shows the latter to be the case, revealing that numerous young, white-hot stars---easily visible in the color picture---are contained within N 81.  This crucial information bears strongly on theories of star formation, and N 81 offers a singular opportunity for a close-up look at the turbulent conditions accompanying the birth of massive stars. The brightest stars in the cluster have a luminosity equal to 300,000 stars like our own Sun. Astronomers are especially keen to study star formation in the Small Magellanic Cloud, because its chemical composition is different from that of the Milky Way. All of the chemical elements, other than hydrogen and helium, have only about one-tenth the abundances seen in our own galaxy.   The study of N 81 thus provides an excellent template for studying the star formation that occurred long ago in very distant galaxies, before nuclear reactions inside stars had synthesized the elements heavier than helium.   The Small Magellanic Cloud, named after the explorer Ferdinand Magellan, lies 200,000 light-years away, and is visible only from the Earth's southern hemisphere. N 81 is the 81st nebula cataloged in a survey of the SMC carried out in the 1950's by astronomer Karl Henize, who later became an astronomer-astronaut who flew into space aboard NASA's space shuttle.   The Hubble Heritage image of N 81 is a color representation of data taken in September, 1997, with Hubble's Wide Field Planetary Camera 2. Color filters were used to sample light emitted by oxygen ([O III]) and hydrogen (H-alpha, H-beta).   N 81 is the target of investigations by European astronomers Mohammad Heydari-Malayeri from the Paris Observatory in France; Michael Rosa from the Space Telescope-European Coordinating Facility in Munich, Germany; Hans Zinnecker of the Astrophysical Institute in Potsdam, Germany; Lise Deharveng of Marseille Observatory, France; and Vassilis Charmadaris of Cornell University, USA (formerly at Paris Observatory). Members of this team are interested in understanding the formation of hot, massive stars, especially under conditions different from those in the Milky Way.   Image Credit: NASA and The Hubble Heritage Team (STScI/AURA) Acknowledgment: Mohammad Heydari-Malayeri (Paris Observatory, France)

A Giant Star Factory in Neighboring Galaxy NGC 6822 Resembling curling flames from a campfire, this magnificent nebula in a neighboring galaxy is giving astronomers new insight into the fierce birth of stars as it may have more commonly happened in the early universe. The glowing gas cloud, called Hubble-V, has a diameter of about 200 light-years. A faint tail of nebulosity trailing off the top of the image sits opposite a dense cluster of bright stars at the bottom of the irregularly shaped nebula. NASA's Hubble Space Telescope's resolution and ultraviolet sensitivity reveals a dense knot of dozens of ultra-hot stars nestled in the nebula, each glowing 100,000 times brighter than our Sun. These youthful 4-million-year-old stars are too distant and crowded together to be resolved from ground-based telescopes. The small, irregular host galaxy, called NGC 6822, is one of the Milky Way's closest neighbors and considered prototypical of the earliest fragmentary galaxies that inhabited the young universe. The galaxy is 1.6 million light-years away in the constellation Sagittarius.    The Hubble-V image data was taken with Hubble's Wide Field Planetary Camera 2 (WFPC2) by two science teams: C. Robert O'Dell of Vanderbilt University and collaborators, and Luciana Bianchi of Johns Hopkins University and Osservatorio Astronomico, Torinese, Italy, and collaborators. This color image was produced by The Hubble Heritage Team (STScI). A Hubble image of Hubble-X, another intense star-forming region in NGC 6822, was released by The Heritage Team in January 2001.

THE GLOWING EYE OF NGC 6751 Astronomers using NASA's Hubble Space Telescope have obtained images of the strikingly unusual planetary nebula, NGC 6751. Glowing in the constellation Aquila like a giant eye, the nebula is a cloud of gas ejected several thousand years ago from the hot star visible in its center.   "Planetary nebulae" are named after their round shapes as seen visually in small telescopes, and have nothing else to do with planets. They are shells of gas thrown off by stars of masses similar to that of our own Sun, when the stars are nearing the ends of their lives. The loss of the outer layers of the star into space exposes the hot stellar core, whose strong ultraviolet radiation then causes the ejected gas to fluoresce as the planetary nebula. Our own Sun is predicted to eject its planetary nebula some 6 billion years from now.   The Hubble observations were obtained in 1998 with the Wide Field Planetary Camera 2 (WFPC2) by a team of astronomers led by Arsen Hajian of the U.S. Naval Observatory in Washington, DC. The Hubble Heritage team, working at the Space Telescope Science Institute in Baltimore, has prepared this color rendition by combining the Hajian team's WFPC2 images taken through three different color filters that isolate nebular gases of different temperatures.   The nebula shows several remarkable and poorly understood features. Blue regions mark the hottest glowing gas, which forms a roughly circular ring around the central stellar remnant. Orange and red show the locations of cooler gas. The cool gas tends to lie in long streamers pointing away from the central star, and in a surrounding, tattered-looking ring at the outer edge of the nebula. The origin of these cooler clouds within the nebula is still uncertain, but the streamers are clear evidence that their shapes are affected by radiation and stellar winds from the hot star at the center. The star's surface temperature is estimated at a scorching 140,000 degrees Celsius (250,000 degrees Fahrenheit).   Hajian and his team are scheduled to re-observe NGC 6751 with Hubble's WFPC2 in 2001. Due to the expansion of the nebula, at a speed of about 40 kilometers per second (25 miles per second), the high resolution of Hubble's camera will reveal the slight increase in the size of the nebula since 1998. This measurement will allow the astronomers to calculate an accurate distance to NGC 6751. In the meantime, current estimates are that NGC 6751 is roughly 6,500 light-years from Earth. The nebula's diameter is 0.8 light-years, some 600 times the diameter of our own solar system.

Blowing Cosmic Bubbles  This NASA Hubble Space Telescope image reveals one of the most bizarre objects in the sky. And.. it just so happens to be located in this weeks constellation, Cassiopeia. This expanding shell of glowing gas surrounds a hot, massive star in our own Milky Way Galaxy. This shell is being shaped by strong stellar winds of material and radiation produced by the bright star at the left, which is 10 to 20 times more massive than our Sun. These fierce winds are sculpting the surrounding material - composed of gas and dust - into the curve-shaped bubble. Astronomers have dubbed it the Bubble Nebula (NGC 7635). The nebula is 10 light-years across, more than twice the distance from Earth to the nearest star. Only part of the bubble is visible in this image. The glowing gas in the lower right-hand corner is a dense region of material that is getting blasted by radiation from the Bubble Nebula's massive star. The radiation is eating into the gas, creating finger-like features. This interaction also heats up the gas, causing it to glow. Scientists study the Bubble Nebula to understand how hot stars interact with the surrounding material.   In case you're interested (of course you are)  NGC 7635 is mag8.5. This is well within the range of amateur telescopes. It is found by following the line extending from alpha through beta Cassiopeia almost to the western border with Cephus. Obviously your views won't match that of Hubble's... but anytime you can view an object that is 11,000+ light years away, you've accomplished something!

IC 418: The "Spirograph" Nebula  NASA's Hubble Space Telescope snapped this remarkable view of the planetary nebula IC418. Glowing like a multi-faceted jewel, IC418 lies about 2,000 light-years from Earth in the direction of the constellation Lepus. This photograph is one of the latest from NASA's Hubble Space Telescope, obtained with the Wide Field Planetary Camera 2.     A planetary nebula represents the final stage in the evolution of a star similar to our Sun. The star at the center of IC 418 was a red giant a few thousand years ago, but then ejected its outer layers into space to form the nebula, which has now expanded to a diameter of about 0.2 light-year. The stellar remnant at the center is the hot core of the red giant, from which ultraviolet radiation floods out into the surrounding gas, causing it to fluoresce. Over the next several thousand years, the nebula will gradually disperse into space, and then the star will cool and fade away for billions of years as a white dwarf. Our own Sun is expected to undergo a similar fate, but fortunately this will not occur until some 5 billion years from now.  The Hubble image of IC 418 is shown in a false-color representation, based on Wide Field Planetary Camera 2 exposures taken in February and September, 1999, through filters that isolate light from various chemical elements. Red shows emission from ionized nitrogen (the coolest gas in the nebula, located furthest from the hot nucleus), green shows emission from hydrogen, and blue traces the emission from ionized oxygen (the hottest gas, closest to the central star). The remarkable textures seen in the nebula are newly revealed by the Hubble telescope, and their origin is still uncertain.

Planetary Nebula Mz3 NASA's Hubble Space Telescope snapped this remarkable view of Planetary Nebula Mz3. Also known as the "Ant Nebula", this beautiful image reveals two distinct lobes emanating from the dying central star.  Astronomers are wondering how a spherical star can produce such varied, non-spherical nebula. Hmmm.... I have no idea... but it sure looks awesome :) Actually, current thinking points towards the possibility of a closely orbiting companion star. This stars gravitational influence would alter the flow and direction of ejected gas.

Rising from a sea of dust and gas like a giant seahorse, the Horsehead nebula is one of the most photographed objects in the sky. NASA's Hubble Space Telescope took a close-up look at this heavenly icon, revealing the cloud's intricate structure. This detailed view of the horse's head was released to celebrate the orbiting observatory's eleventh anniversary. Produced by the Hubble Heritage Project, this picture is a testament to the Horsehead's popularity. Internet voters selected this object for the orbiting telescope to view.  The Horsehead, also known as Barnard 33, is a cold, dark cloud of gas and dust, silhouetted against the bright nebula, IC 434. The bright area at the top left edge is a young star still embedded in its nursery of gas and dust. But radiation from this hot star is eroding the stellar nursery. The top of the nebula also is being sculpted by radiation from a massive star located out of Hubble's field of view.