Astronomers using NASA's Spitzer Space telescope have found a likely solution to a centuries-old riddle of the night sky. Every 27 years, a bright star called Epsilon Aurigae fades over period of two years, then brightens back up again. Though amateur and professional astronomers have observed the system extensively, the nature of both the bright star and the companion object that periodically eclipses it have remained unclear. The companion is known to be surrounded by a dusty disk, as illustrated in this artist's concept. Data from Spitzer turned out to be the missing puzzle piece. Spitzer's infrared vision revealed the size of the dusty disk that swirls around the companion object. When astronomers plugged this size information into a model of the system, they were able to rule out the theory that the main bright star is a supergiant. Instead, it is a bright star with a lot less mass. The new model also holds that the companion object is a so-called "B star" circled by a dusty disk.

This graph of data from multiple telescopes shows the distribution of light from a pair of stars known as Epsilon Aurigae. For centuries, astronomers had not been able to figure out the nature of this "eclipsing binary system," in which a bright naked-eye star is eclipsed by a companion object every 27 years. Data from NASA's Spitzer Space Telescope are pointing to a solution to this age-old riddle. The Spitzer data, shown in bright yellow and orange, provide the missing puzzle pieces need to fit all the data on the star together into a neat model. The blue data show ultraviolet observations, and the light yellow/green data are from visible-light telescopes. The blue data show light from the companion object, a so-called B star, while the light yellow data show light from the main bright star, called an F star. The orange and bright yellow data from Spitzer show light from the F star and a dusty disk that is surrounding the B-star. The new model indicates that the F star is not a supergiant as a favored theory had proposed but a dying star with a lot less mass.

This composite graphic encompasses a quarter century of infrared astronomy from space, a world away from Galileo Galilei's eight-power telescope that was the cutting edge of astronomy 400 years ago. The composite recognizes the International Year of Astronomy and celebrates the dramatic progress in our understanding of the universe derived from infrared observations. It also illustrates some of the contributions from the Infrared Processing and Analysis Center (IPAC) to this progress by way of astronomical data processing, analysis, archiving and dissemination. Infrared astronomy, especially from space, explores up a vast portion of the spectrum beyond the red end of visible light. Through this window the universe emits a tremendous variety of information about the physical and chemical composition of various regions, about their energetic states, and about the current and historical activity of star formation. Infrared and submillimeter wavelengths still hold the most promise for studying the earliest moments in the history of the universe when diffuse gas was transformed into the first stars and galaxies. This era is thought to have occurred around the first percent of the age of the universe. While celebrating this rich legacy of infrared astronomy, infrared astronomers are also enjoying a golden age of sorts, with an unprecedented number of missions currently in-flight: NASA's Spitzer Space Telescope is continuing its warm mission; the European Space Agency Herschel and Planck telescopes are in their prime mission phase; NASA's Wide Field Infrared Survey Explorer (WISE) just launched and is expected to start mapping the sky in early 2010. All of these missions have links to IPAC. "Rho Ophiuchi" is a complex region of star formation centered on a large cloud of molecular gas, and located about 400 light-years from Earth. Hundreds of young stars are forming out of the central cloud. Their typical age is 300,000 years, seen in the first "moments" of the billions of years in a star's life span. IRAS, the InfraRed Astronomical Satellite, was a joint project between the U.S., the Netherlands and the United Kingdom. It operated in Earth orbit from 25 January to 22 November 1983, surveying the infrared sky and dramatically expanding our understanding of the Universe by revealing surprising new phenomena. This false-color image renders infrared light into visible light, showing 12 m emission as blue, 25 and 60 m as green, and 100 m as red. The infrared emission originates in cosmic dust at a range of temperatures, with the colder dust appearing redder in this image. The field of view is about 18 degrees to a side. The small grey inset is amplified into the views shown in the remaining three frames. IPAC was established twenty-five years ago on the campus of the California Institute of Technology to provide expertise and support for the processing, analysis and interpretation of data from IRAS. ISO, the Infrared Space Observatory, was a European Space Agency project with Japanese and U.S. participation, and operated from 17 November 1995 to 16 May 1998. The image shows 7 m emission in blue and 15 m in red, revealing very small dust grains heated by stars as diffuse emission, and very young stars still in the formation stages as the reddish points, whereas older stars appear as blue dots. The field of view is the same as shown for 2MASS and Spitzer, about 3/4 of a degree on a side. The scientific and technical expertise of the IPAC staff was one of the many heritages from IRAS, prompting NASA to designate IPAC as the U.S. science support center for ISO. 2MASS, the Two Micron All-Sky Survey, a U.S. National Aeronautics and Space Administration and National Science Foundation project, gathered data from June 1997 to February 2001, mapping the whole sky in the near infrared from the ground. The picture shows 1.3 m emission as blue, 1.6 m as green, and 2.2 m as red. The sky appears dark towards dense parts of the cloud because dust absorbs the light, whereas the reddish sources signal young stars. The field of view is about 3/4 of a degree on a side. Its unique capabilities made IPAC the obvious choice for processing the many terabytes of data from 2MASS. The University of Massachusetts developed and operated the two observatories that acquired the data. IPAC's role included design of survey strategy, data processing, quality control, and the production of final catalogs and final data products from the primary survey and the extended mission. The Spitzer Space Telescope is an infrared observatory built and operated by the Jet Propulsion Laboratory of the California Institute of Technology for the U.S. National Aeronautics and Space Administration. It was launched on 25 August 2003 into a Sun-centered orbit, and ran out of the liquid helium that kept it cold on 15 May 2005. Today, it still observes the cosmos at 3.6 and 4.5 m, using one out of three original instruments. The picture shows 3.6 m emission as blue, 8 m as green, and 24 m as red. Dust glows with different colors depending on its composition and heating, whereas the colors of the stars indicate their age, blue for mature stars, and red for those still surrounded by natal cloud material. The field of view is again about 3/4 of a degree on a side. In early 1998, IPAC was designated as the science operations center for the Spitzer Space Telescope, NASA's Infrared Great Observatory. The Spitzer Science Center (SSC), is an autonomously managed entity within IPAC, which relies on the skills and knowledge of IPAC experts in supporting Spitzer.

This image shows two young brown dwarfs, objects that fall somewhere between planets and stars in terms of their temperature and mass. Brown dwarfs are cooler and less massive than stars, never igniting the nuclear fires that power their larger cousins, yet they are more massive (and normally warmer) than planets. When brown dwarfs are born, they heat the nearby gas and dust, which enables powerful infrared telescopes like NASA's Spitzer Space Telescope to detect their presence. Here we see a long sought-after view of these very young objects, labeled as A and B, which appear as closely-spaced purple-blue and orange-white dots at the very center of this image. The surrounding envelope of cool dust surrounding this nursery can be seen in purple. These twins, which were found in the region of the Taurus-Auriga star-formation complex, are the youngest of their kind ever detected. They are also helping astronomers solve a long-standing riddle about how brown dwarfs are formed more like stars or more like planets? Based on these findings, the researchers think they have found the answer: Brown dwarfs form like stars. This image combined data from three different telescopes on the ground and in space. Near-infrared observations collected at the Calar Alto Observatory in Spain cover wavelengths of 1.3 and 2.2 microns (rendered as blue). Spitzer's infrared array camera contributed the 4.5-micron (green) and 8.0-micron (yellow) observations, and its multiband imaging photometer added the 24-micron (red) component. The Caltech Submillimeter Observatory in Hawaii made the far-infrared observations at 350 microns (purple). These observations were made before Spitzer ran out its coolant in May of 2009, officially beginning its "warm" mission.

This artist's rendering gives us a glimpse into a cosmic nursery as a star is born from the dark, swirling dust and gas of this cloud. Stars form when dark dust from the cloud begins to clump together under the influence of its own gravity. The infalling material forms a disk as it spirals inward, which feeds material onto the forming star at its center. Jets of material that shoot from the inner disk and protostar herald its birth. Planets form out of the remnants of the disk of material that surrounds the infant star. This leads to a question that has long perplexed astronomers about the nature of brown dwarfs, objects that fall between planets and stars in terms of their temperature and mass. Are brown dwarfs born like stars, as in this rendering, or do they form like planets orbiting another star? A study by researchers using data from NASA's Spitzer Space Telescope has led to the preliminary conclusion that they are formed much like the star you see here.

This image shows two young brown dwarfs, objects that fall somewhere between planets and stars in terms of their temperature and mass. Brown dwarfs are cooler and less massive than stars, never igniting the nuclear fires that power their larger cousins, yet they are more massive (and normally warmer) than planets. When brown dwarfs are born, they heat the nearby gas and dust, which enables powerful infrared telescopes like NASA's Spitzer Space Telescope to detect their presence. Here we see a long sought-after view of these very young objects, labeled as A and B, which appear as closely-spaced purple-blue and orange-white dots at the very center of this image. The surrounding envelope of cool dust surrounding this nursery can be seen in purple. These twins, which were found in the region of the Taurus-Auriga star-formation complex, are the youngest of their kind ever detected. They are also helping astronomers solve a long-standing riddle about how brown dwarfs are formed more like stars or more like planets? Based on these findings, the researchers think they have found the answer: Brown dwarfs form like stars. This image combined data from three different telescopes on the ground and in space. Near-infrared observations collected at the Calar Alto Observatory in Spain cover wavelengths of 1.3 and 2.2 microns (rendered as blue). Spitzer's infrared array camera contributed the 4.5-micron (green) and 8.0-micron (yellow) observations, and its multiband imaging photometer added the 24-micron (red) component. The Caltech Submillimeter Observatory in Hawaii made the far-infrared observations at 350 microns (purple). These observations were made before Spitzer ran out its coolant in May of 2009, officially beginning its "warm" mission.

A star's spectacular death in the constellation Taurus was observed on Earth as the supernova of 1054 A.D. Now, almost a thousand years later, a super dense object -- called a neutron star -- left behind by the explosion is seen spewing out a blizzard of high-energy particles into the expanding debris field known as the Crab Nebula. X-ray data from Chandra provide significant clues to the workings of this mighty cosmic "generator," which is producing energy at the rate of 100,000 suns. This composite image uses data from three of NASA's Great Observatories. The Chandra X-ray image is shown in blue, the Hubble Space Telescope optical image is in red and yellow, and the Spitzer Space Telescope's infrared image is in purple. The X-ray image is smaller than the others because extremely energetic electrons emitting X-rays radiate away their energy more quickly than the lower-energy electrons emitting optical and infrared light. Along with many other telescopes, Chandra has repeatedly observed the Crab Nebula over the course of the mission's lifetime. The Crab Nebula is one of the most studied objects in the sky, truly making it a cosmic icon.

NASA's Spitzer Space Telescope captured this infrared image of a giant halo of very fine dust around the young star HR 8799, located 129 light-years away in the constellation Pegasus. The brightest parts of this dust cloud (yellow-white) likely come from the outer cold disk similar to our own Kuiper belt (beyond Neptune's orbit). The huge extended dust halo is seen as orange-red. Astronomers think that the three large planets known to orbit the star are disturbing small comet-like bodies, causing them to collide and kick up dust. The extended dust halo has a diameter of about 2,000 astronomical units, or 2,000 times the distance between Earth and the sun. For reference, the size of Pluto's orbit is tiny by comparison, with a diameter of about 80 astronomical units. This image was captured by Spitzer's multiband imaging photometer at an infrared wavelength of 70 microns in Jan. 2009.

This artist's conception shows a lump of material in a swirling, planet-forming disk. Astronomers using NASA's Spitzer Space Telescope found evidence that a companion to a star -- either another star or a planet -- could be pushing planetary material together, as illustrated here. Planets are born out of spinning disks of gas and dust. They can carve out lanes or gaps in the disks as they grow bigger and bigger. Scientists used Spitzer's infrared vision to study the disk around a star called LRLL 31, located about 1,000 light-years away in the IC 348 region of the constellation Perseus. Spitzer's new infrared observations reveal that the disk has both an inner and outer gap. What's more, the data show that infrared light from the disk is changing over as little time as one week -- a very unusual occurrence. In particular, light of different wavelengths seesawed back and forth, with short-wavelength light going up when long-wavelength light went down, and vice versa. According to astronomers, this change could be caused by a companion to the star (illustrated as a planet in this picture). As the companion spins around, its gravity would cause the wall of the inner disk to squeeze into a lump. This lump would also spin around the star, shadowing part of the outer disk. When the bright side of the lump is on the far side of the star, and facing Earth, more infrared light at shorter wavelengths should be observed (hotter material closer to the star emits shorter wavelengths of infrared light). In addition, the shadow of the lump should cause longer-wavelength infrared light from the outer disk to decrease. The opposite would be true when the lump is in front of the star and its bright side is hidden (shorter-wavelength light would go down, and longer-wavelength light up). This is precisely what Spitzer observed. The size of the lump and the planet have been exaggerated to better illustrate the dynamics of the system.

This composite image, combining data from NASA's Chandra X-ray Observatory and Spitzer Space Telescope shows the star-forming cloud Cepheus B, located in our Milky Way galaxy about 2,400 light years from Earth. A molecular cloud is a region containing cool interstellar gas and dust left over from the formation of the galaxy and mostly contains molecular hydrogen. The Spitzer data, in red, green and blue shows the molecular cloud (in the bottom part of the image) plus young stars in and around Cepheus B, and the Chandra data in violet shows the young stars in the field. The Chandra observations allowed the astronomers to pick out young stars within and near Cepheus B, identified by their strong X-ray emission. The Spitzer data showed whether the young stars have a so-called "protoplanetary" disk around them. Such disks only exist in very young systems where planets are still forming, so their presence is an indication of the age of a star system. These data provide an excellent opportunity to test a model for how stars form. The new study suggests that star formation in Cepheus B is mainly triggered by radiation from one bright, massive star (HD 217086) outside the molecular cloud. According to the particular model of triggered star formation that was tested -- called the radiation- driven implosion model -- radiation from this massive star drives a compression wave into the cloud triggering star formation in the interior, while evaporating the cloud's outer layers. Different types of triggered star formation have been observed in other environments. For example, the formation of our solar system was thought to have been triggered by a supernova explosion. In the star-forming region W5, a "collect-and-collapse" mechanism is thought to apply, where shock fronts generated by massive stars sweep up material as they progress outwards. Eventually the accumulated gas becomes dense enough to collapse and form hundreds of stars. The radiation-driven implosion model mechanism is also thought to be responsible for the formation of dozens of stars in W5. The main cause of star formation that does not involve triggering is where a cloud of gas cools, gravity gets the upper hand, and the cloud falls in on itself.

This composite image, combining data from NASA's Chandra X-ray Observatory and Spitzer Space Telescope shows the star-forming cloud Cepheus B, located in our Milky Way galaxy about 2,400 light years from Earth. A molecular cloud is a region containing cool interstellar gas and dust left over from the formation of the galaxy and mostly contains molecular hydrogen. The Spitzer data, in red, green and blue shows the molecular cloud (in the bottom part of the image) plus young stars in and around Cepheus B, and the Chandra data in violet shows the young stars in the field. The Chandra observations allowed the astronomers to pick out young stars within and near Cepheus B, identified by their strong X-ray emission. The Spitzer data showed whether the young stars have a so-called "protoplanetary" disk around them. Such disks only exist in very young systems where planets are still forming, so their presence is an indication of the age of a star system. These data provide an excellent opportunity to test a model for how stars form. The new study suggests that star formation in Cepheus B is mainly triggered by radiation from one bright, massive star (HD 217086) outside the molecular cloud. According to the particular model of triggered star formation that was tested -- called the radiation- driven implosion model -- radiation from this massive star drives a compression wave into the cloud triggering star formation in the interior, while evaporating the cloud's outer layers. Different types of triggered star formation have been observed in other environments. For example, the formation of our solar system was thought to have been triggered by a supernova explosion. In the star-forming region W5, a "collect-and-collapse" mechanism is thought to apply, where shock fronts generated by massive stars sweep up material as they progress outwards. Eventually the accumulated gas becomes dense enough to collapse and form hundreds of stars. The radiation-driven implosion model mechanism is also thought to be responsible for the formation of dozens of stars in W5. The main cause of star formation that does not involve triggering is where a cloud of gas cools, gravity gets the upper hand, and the cloud falls in on itself.

This artist's concept shows a celestial body about the size of our moon slamming at great speed into a body the size of Mercury. NASA's Spitzer Space Telescope found evidence that a high-speed collision of this sort occurred a few thousand years ago around a young star, called HD 172555, still in the early stages of planet formation. The star is about 100 light-years from Earth. Spitzer detected the signatures of vaporized and melted rock, in addition to rubble, all flung out from the giant impact. Further evidence from the infrared telescope shows that these two bodies must have been traveling at a velocity relative to each other of at least 10 kilometers per second (about 22,400 miles per hour). As the bodies slammed into each other, a huge flash of light would have been emitted. Rocky surfaces were vaporized and melted, and hot matter was sprayed everywhere. Spitzer detected the vaporized rock in the form of silicon monoxide gas, and the melted rock as a glassy substance called obsidian. On Earth, silica can be found around volcanoes in black glassy rocks called obsidian, and around meteor craters in small rocks called tektites. Shock waves from the collision would have traveled through the planet, throwing rocky rubble into space. Spitzer also detected the signatures of this rubble. In the end, the larger planet is left skinned, stripped of its outer layers. The core of the smaller body and most of its surface were absorbed by the larger one. This merging of rocky bodies is how planets like Earth are thought to form. Astronomers say a similar type of event stripped Mercury of its crust early on in the formation of our solar system, flinging the removed material away from Mercury, out into space and into the sun. Our moon was also formed by this type of high-speed impact: a body the size of Mars is thought to have slammed into a young Earth about 30 to 100 million years after the sun formed. The sun is now 4.5 billion years old. According to this theory, the resulting molten rock, vapor and shattered debris mixed with debris from Earth to form a ring around our planet. Over time, this debris coalesced to make the moon.

This spectrum, or plot of infrared data, from NASA's Spitzer Space telescope reveals the presence of vaporized and melted rock, along with rubble, around a young, hot star. The star, called HD 172555, is about twice the mass of the sun and about 100 light-years away. The data indicate that two bodies at least as big as our moon slammed into each other in a high-speed collision around the star. Impacts of this sort are normal part of the growth process of rocky planets like Earth. Infrared light, or heat radiation, comes from materials around a star that are warmed by starlight. These materials re-radiate the light at characteristic wavelengths unique to the chemical composition of the material, allowing astronomers to figure out what kind of stuff is in orbit around a star, even from many light-years away. In the case of the this spectrum, there are strong, wide peaks at 4 and 8 microns due to silicon monoxide (SiO) gas, formed when rock is heated so much it evaporates. The much larger and sharper peak centered at 9.3 microns is characteristic of amorphous glassy silica (a material similar to quartz or window glass), which is formed when rock is melted and then refrozen. When the rock is refrozen quickly it forms a substance called tektite; when is cools over minutes to hours, it becomes obsidian. The long, slow rise and plateau from 14 to 35 microns is from thick, pebble-size or larger cold rocks -- essentially rubble. The total brightness of the spectrum indicates that the colliding bodies must have both been at least as big as our moon. The shape of the rubble feature tells us that the large pieces of rock are at about 200 Kelvin (about minus 100 degrees Fahrenheit), and about 5.8 astronomical units from the star (one astronomical unit is the distance between Earth and the sun).

These images are some of the first to be taken during Spitzer's warm mission -- a new phase that began after the telescope, which operated for more than five-and-a-half years, ran out of liquid coolant. The pictures were snapped with the two infrared channels that still work at Spitzer's still-quite-chilly temperature of 30 Kelvin (about minus 406 Fahrenheit). The two infrared channels are part of Spitzer's infrared array camera: 3.6-micron light is blue and 4.5-micron light is orange. The main picture shows a cloud, known as DR22, bursting with new stars in the Cygnus region of the sky. Spitzer's infrared eyes can both see through and see dust, giving it a unique view into star-forming nests. The blue areas are dusty clouds, and the orange is mainly hot gas. The picture at upper right shows a relatively calm galaxy called NGC 4145. This galaxy has already made most of its stars and has little star-forming activity. It is located 68 million light-years away in the constellation Canes Venatici. Blue shows starlight and dust. The final picture at lower right shows a dying star called NGC 4361. This star was once a lot like our sun, before it evolved and puffed out its outer layers. The object, called a planetary nebula, is unusual in that is has four lobes, or jets, of ejected material instead of the standard two. Astronomers suspect the there might be two dying stars inside the nebula, each producing a bipolar jet. Orange primarily shows heated gas. The new pictures were taken while the telescope was being re-commissioned, on July 18 (NGC 4145, NGC 4361) and July 21 (Cygnus).

This infrared picture shows a cloud, known as DR22, bursting with new stars in the Cygnus region of the sky. Spitzer's infrared eyes can both see through and see dust, giving it a unique view into star-forming nests. The blue areas are dusty clouds, and the orange is mainly hot gas. This image is one of the first to be taken during Spitzer's warm mission -- a new phase that began after the telescope, which operated for more than five-and-a-half years, ran out of liquid coolant. The picture was snapped with the two infrared channels that still work at Spitzer's still-quite-chilly temperature of 30 Kelvin (about minus 406 Fahrenheit). The two infrared channels are part of Spitzer's infrared array camera: 3.6-micron light is blue and 4.5-micron light is orange. This picture was taken while the telescope was being re-commissioned, on July 21.

These data from NASA's Spitzer Space Telescope reveal a newborn star at the center of our Milky Way. Our galaxy's core is a frenzied place, and identifying baby stars there has been difficult. Dust standing between us and the core blocks visible light, but infrared light, as detected by Spitzer, can get through. To definitively identify newborn stars, astronomers used Spitzer's spectrograph to break starlight up into its basic infrared components. The resulting data, called as spectrum, are shown here for a single star, with signatures of key molecules labeled. Acetylene, hydrogen cyanide and carbon dioxide are all gases known to be associated with newborn stars in other parts of our galaxy. They are produced when young stars heat up gas in their outer envelope. The broad dry ice feature is also characteristic of newborn stars. Spitzer found results for two other stars whose data are not shown here.

This infrared image from NASA's Spitzer Space Telescope shows three baby stars in the bustling center of our Milky Way galaxy. The three stars are the first to be discovered in the region -- previous attempts to find them were unsuccessful because there is so much dust standing between us and our galaxy's core. Spitzer was able to find the newborns with its sharp infrared eyes, which can cut through dust. The center of our galaxy is a hectic place. It's stuffed with stars, gas and dust. Astronomers have long wondered how stars can form in such chaotic circumstances. While they have known that stars are born there, they weren't able to see the stars forming until now. Astronomers plan to search for more newborn stars in the region, and ultimately learn more about stellar births at the center of the Milky Way.

This artist's concept illustrates how silicate crystals like those found in comets can be created by an outburst from a growing star. The image shows a young sun-like star encircled by its planet-forming disk of gas and dust. The silicate that makes up most of the dust would have begun as non-crystallized, amorphous particles. Streams of material are seen spiraling from the disk onto the star increasing its mass and causing the star to brighten and heat up dramatically. The outburst causes temperatures to rise in the star's surrounding disk. When the disk warms from the star's outburst, the amorphous particles of silicate melt. As they cool off, they transform into forsterite, a type of silicate crystal often found in comets in our solar system. In April 2008, NASA's Spitzer Space Telescope detected evidence of this process taking place on the disk of a young sun-like star called EX Lupi.

Astronomers have had a rare opportunity to witness the creation of silicate crystals around a young star, as seen in this data plot from NASA's Spitzer Space Telescope. The two lines in this chart are from Spitzer's spectrograph, which collects light and sorts it according to color, or wavelength. They show the emission from dust grains in the protoplanetary disk surrounding a young star known as EX Lupi. The blue line dates from an early observation made on 18 March, 2005. The hump is a characteristic spectral feature typical of dust particles found throughout interstellar space. The green line is a later observation, made on 21 April, 2008, taken while the star was experiencing an outburst, or eruption. The green area under the curve highlights a new feature that matches the spectral signature of silicate crystals (pictured in the inset). Astronomers believe these observations indicate that the crystals were newly-forged in the warm glow of the outburst. The star brightened and heated up as material fell onto its surface from its surrounding disk, a process by which young stars increase their mass. When the surrounding disk warms from the star's outburst, the amorphous particles of silicate melt. As they cool off, they transform into forsterite, a type of silicate crystal often found in comets in our solar system. The two observations have been matched in scaling to highlight the new forsterite feature, observed while the star was declining in brightness. At the time of the second observation, EX Lupi was still 30 times brighter in visible light than during its quiet periods.

This artist's concept illustrates how silicate crystals like those found in comets can be created by an outburst from a growing star. The image shows a young sun-like star encircled by its planet-forming disk of gas and dust. The silicate that makes up most of the dust would have begun as non-crystallized, amorphous particles. Streams of material are seen spiraling from the disk onto the star increasing its mass and causing the star to brighten and heat up dramatically. The outburst causes temperatures to rise in the star's surrounding disk. When the disk warms from the star's outburst, the amorphous particles of silicate melt. As they cool off, they transform into forsterite (see inset), a type of silicate crystal often found in comets in our solar system. In April 2008, NASA's Spitzer Space Telescope detected evidence of this process taking place on the disk of a young sun-like star called EX Lupi.

This chart shows the brightness and wavelength of the radiation coming from white dwarf GD 16 and its associated disk of closely orbiting rocky material. The data was obtained with NASA's Spitzer Space Telescope. The colored data points indicate hot emission from the white dwarf (left of the graph) and cool emission from the surrounding material (right hand side). White dwarfs are the remnants of relatively low-mass stars that have passed through their red giant stage. A white dwarf may be the size of the Earth, but contain the same mass as the Sun. This star remnant is so dense, in fact, that one teaspoon of white dwarf material would weigh several tons. Over 90% of all stars -- including our Sun -- will end their lives as white dwarfs.

This artist's conception shows a young, hypothetical planet around a cool star. A soupy mix of potentially life-forming chemicals can be seen pooling around the base of the jagged rocks. Observations from NASA's Spitzer Space Telescope hint that planets around cool stars -- the so-called M-dwarfs and brown dwarfs that are widespread throughout our galaxy -- might possess a different mix of life-forming, or prebiotic, chemicals than our young Earth. Life on our planet is thought to have arisen out of a pond-scum-like mix of chemicals. Some of these chemicals are thought to have come from a planet-forming disk of gas and dust that swirled around our young sun. Meteorites carrying the chemicals might have crash-landed on Earth. Astronomers don't know if these same life-generating processes are taking place around stars that are cooler than our sun, but the Spitzer observations show their disk chemistry is different. Spitzer detected a prebiotic molecule, called hydrogen cyanide, in the disks around yellow stars like our sun, but found none around cooler, less massive, reddish stars. Hydrogen cyanide is a carbon-containing, or organic compound. Five hydrogen cyanide molecules can join up to make adenine -- a chemical element of the DNA molecule found in all living organisms on Earth.

NASA's Spitzer Space Telescope detected a prebiotic, or potentially life-forming, molecule called hydrogen cyanide (HCN) in the planet-forming disks around yellow stars like our sun, but not in the disks around cooler, reddish stars. The observations are plotted in this graph, called a spectrum, in which light from the gas in the disks around the stars has been split up into its basic components, or wavelengths. Data from stars like our sun are yellow, and data from cool stars are orange. Light wavelengths are shown on the X-axis, and the relative brightness of disk emission is shown on the Y-axis. The signature of a baseline molecule, called acetylene (C2H2), was seen for both types of stars, but hydrogen cyanide was seen only around stars like our sun. Hydrogen cyanide is an organic, nitrogen-containing molecule. Five hydrogen cyanide molecules can link up to form adenine, one of the four chemical bases of DNA.

NASA's Spitzer Space Telescope set its infrared eyes upon the dusty remains of shredded asteroids around several dead stars. This artist's concept illustrates one such dead star, or "white dwarf," surrounded by the bits and pieces of a disintegrating asteroid. These observations help astronomers better understand what rocky planets are made of around other stars. Asteroids are leftover scraps of planetary material. They form early on in a star's history when planets are forming out of collisions between rocky bodies. When a star like our sun dies, shrinking down to a skeleton of its former self called a white dwarf, its asteroids get jostled about. If one of these asteroids gets too close to the white dwarf, the white dwarf's gravity will chew the asteroid up, leaving a cloud of dust. Spitzer's infrared detectors can see these dusty clouds and their various constituents. So far, the telescope has identified silicate minerals in the clouds polluting eight white dwarfs. Because silicates are common in our Earth's crust, the results suggest that planets similar to ours might be common around other stars.

This plot of data from NASA's Spitzer Space Telescopes shows that asteroid dust around a dead "white dwarf" star contains silicates -- a common mineral on Earth. The data were taken primarily by Spitzer's infrared spectrograph, an instrument that breaks light apart into its basic constituents. The yellow dots show averaged data from the spectrograph, while the orange triangles show older data from Spitzer's infrared array camera. The white dwarf is called GD 40.

This image from NASA's Spitzer Space Telescope shows the nasty effects of living near a group of massive stars: radiation and winds from the massive stars (white spot in center) are blasting planet-making material away from stars like our sun. The planetary material can be seen as comet-like tails behind three stars near the center of the picture. The tails are pointing away from the massive stellar furnaces that are blowing them outward. The picture is the best example yet of multiple sun-like stars being stripped of their planet-making dust by massive stars. The sun-like stars are about two to three million years old, an age when planets are thought to be growing out of surrounding disks of dust and gas. Astronomers say the dust being blown from the stars is from their outer disks. This means that any Earth-like planets forming around the sun-like stars would be safe, while outer planets like Uranus might be nothing more than dust in the wind. This image shows a portion of the W5 star-forming region, located 6,500 light-years away in the constellation Cassiopeia. It is a composite of infrared data from Spitzer's infrared array camera and multiband imaging photometer. Light with a wavelength of 3.5 microns is blue, while light from the dust of 24 microns is orange-red.

This artist's concept shows the dimmest star-like bodies currently known -- twin brown dwarfs referred to as 2M 0939. The twins, which are about the same size, are drawn as if viewed from one side. Brown dwarfs are neither planets nor stars. They form like stars out of collapsing clouds of gas and dust, but they don't have enough mass to ignite nuclear burning in their cores and become full-blown stars. They are similar to Jupiter in that they are cool balls of gas, but they are warmer and heavier. Astronomers say that the universe is littered with these cosmic misfits, but because they are so dim, they are hard to find. NASA's Spitzer Space Telescope is fitted with heat-seeking infrared eyes, which allow it to detect the minute glow of cool objects like brown dwarfs. Data from Spitzer and the Anglo-Australian Observatory in Australia together reveal that both of the brown dwarfs making up 2M 0939 share the title of dimmest known brown dwarfs. Their atmospheres are also among the coolest known for any brown dwarf (565 to 635 Kelvin or 560 to 680 degrees Fahrenheit). The term "brown dwarf" comes from the fact that these objects change color over time, and therefore do not have a definitive color. The 2M 0939 brown dwarfs, if we could see them directly with out eyes, would glow a very dark magenta color, due to their cool temperatures and the presence of water, methane and ammonia gases in their atmospheres. 2M 0939's full name is 2MASS J09393548-2448279 after the partly NASA-funded infrared mission, the Two Micron All Sky Survey, or "2MASS," which first detected the object in 1999.

NASA's Spitzer Space Telescope has captured a new, infrared view of the choppy star-making cloud called M17, also known as the Omega Nebula or the Swan Nebula. The cloud, located about 6,000 light-years away in the constellation Sagittarius, is dominated by a central group of massive stars -- the most massive stars in the region. These central stars give off intense flows of expanding gas, which rush like rivers against dense piles of material, carving out the deep pocket at center of the picture. Winds from the region's other massive stars push back against these oncoming rivers, creating bow shocks like those that pile up in front of speeding boats. Three of these bow shocks are nestled in the upper left side of the central cavity, but are difficult to spot in this view. They are composed of compressed gas in addition to dust that glows at infrared wavelengths Spitzer can see. The smiley-shaped bow shocks curve away from the stellar winds of the central massive stars. This picture was taken with Spitzer's infrared array camera. It is a four-color composite, in which light with a wavelength of 3.6 microns is blue; 4.5-micron light is green; 5.8-micron light is orange; and 8-micron light is red. Dust is red, hot gas is green and white is where gas and dust intermingle. Foreground and background stars appear scattered through the image.

NASA's Spitzer Space Telescope has captured a new, infrared view of the choppy star-making cloud called M17, also known as the Omega Nebula or the Swan Nebula. The cloud, located about 6,000 light-years away in the constellation Sagittarius, is dominated by a central group of massive stars -- the most massive stars in the region (see yellow circle). These central stars give off intense flows of expanding gas, which rush like rivers against dense piles of material, carving out the deep pocket at center of the picture. Winds from the region's other massive stars push back against these oncoming rivers, creating bow shocks like those that pile up in front of speeding boats. Three of these bow shocks are labeled in the magnified inset. They are composed of compressed gas in addition to dust that glows at infrared wavelengths Spitzer can see. The smiley-shaped bow shocks curve away from the stellar winds of the central massive stars. This picture was taken with Spitzer's infrared array camera. It is a four-color composite, in which light with a wavelength of 3.6 microns is blue; 4.5-micron light is green; 5.8-micron light is orange; and 8-micron light is red. Dust is red, hot gas is green and white is where gas and dust intermingle. Foreground and background stars appear scattered through the image.

NASA's Spitzer Space Telescope has, for the first time, detected tiny quartz-like crystals sprinkled in young planetary systems. The crystals, which are types of silica minerals called cristobalite and tridymite, can be seen close-up in the black-and-white insets (cristobalite is on the left, and tridymite on the right). The main picture is an artist's concept of a young star and its swirling disk of planet-forming materials. Cristobalite and tridymite are thought to be two of many planet ingredients. On Earth, they are normally found as tiny crystals in volcanic lava flows and meteorites from space. These minerals are both related to quartz. For example, if you were to heat the familiar quartz crystals often sold as mystical tokens, the quartz would transform into cristobalite and tridymite. Because cristobalite and tridymite require rapid heating and cooling to form, astronomers say they were most likely generated by shock waves traveling through the planetary disks. The insets are Scanning Electron Microscope pictures courtesy of George Rossman of the California Institute of Technology, Pasadena, Calif.