CSIRO Telescope Spots Mega-Star Cradle

Mid-infrared image of BYF 73 from NASA's Spitzer Space Telescope. The yellowish wisps to the right are remnants of gas that have been heated and are being driven off by the massive young stars within them (seen in blue). The large-scale collapse of colder gas to form a massive cluster is centred around the bright stars just to the left of the heated wisps. Image credit - NASA/JPL-Caltech

Using a CSIRO radio telescope, an international team of researchers has caught an enormous cloud of cosmic gas and dust in the process of collapsing in on itself - a discovery which could help solve one of astronomy's enduring conundrums: 'How do massive stars form?'

Dr Peter Barnes from the University of Florida says astronomers have a good grasp of how stars such as our Sun form from clouds of gas and dust, but for heavier stars - ten times the mass of the Sun or more - they are still largely in the dark, despite years of work.

"Astronomers are still debating the physical processes that can generate these big stars," Dr Barnes says.

"Massive stars are rare, making up only a few per cent of all stars, and they will only form in significant numbers when really massive clouds of gas collapse, creating hundreds of stars of different masses. Smaller gas clouds are not likely to make big stars."

Accordingly, regions in space where massive stars seem to be forming are also rare. Most are well over 1000 light-years away, making them hard to observe.

Using CSIRO's 'Mopra' radio telescope - a 22m dish near Coonabarabran, NSW - the research team discovered a massive cloud of mostly hydrogen gas and dust, three or more light-years across, that is collapsing in on itself and will probably form a huge cluster of stars.

Dr Stuart Ryder of the Anglo-Australian Observatory said the discovery was made during a survey of more than 200 gas clouds.

"With clouds like this we can test theories of massive star cluster formation in great detail."

The gas cloud, called BYF73, is about 8,000 light years away, in the constellation of Carina ("the keel") in the Southern sky.

Evidence for 'infalling' gas came from the radio telescope's detection of two kinds of molecules in the cloud - HCO+ and H13CO+. The spectral lines from the HCO+ molecules in particular showed the gas had a velocity and temperature pattern that indicated collapse.

Mopra Research Scientist at CSIRO Astronomy and Space Science, Dr Kate Brooks, said the Mopra telescope excels at giving a picture of the complex chemistry of cosmic gas clouds.

"Much of its time is used for large projects like this, and almost all Mopra projects are international collaborations."

The CSIRO telescope observations were confirmed by observations with the Atacama Submillimeter Telescope Experiment (ATSE) telescope in Chile.

The research team calculates that the gas is falling in at the rate of about three per cent of the Sun's mass every year - one of the highest rates known.

Follow-up infrared observations made with the 3.9-m Anglo-Australian Telescope (also near Coonabarabran, NSW) showed signs of massive young stars that have already formed right at the centre of the gas clump, and new stars forming.

Star-formation in the cloud was also evident in archival data from the Spitzer and MSX spacecraft, which observe in the mid-infrared.

Gas cloud BYF73 was found during a large-scale search for massive star-forming regions - the Census of High- and Medium-mass Protostars, or CHaMP. This is one of the largest, most uniform and least biased surveys to date of massive star-forming regions in our Galaxy.

NASA's Spitzer Space Telescope Discovers Extrasolar Planet Lacking Methane

PASADENA, Calif. - NASA's Spitzer Space Telescope has discovered something odd about a distant planet -- it lacks methane, an ingredient common to many of the planets in our solar system.

"It's a big puzzle," said Kevin Stevenson, a planetary sciences graduate student at the University of Central Florida in Orlando, lead author of a study appearing tomorrow, April 22 in the journal Nature. "Models tell us that the carbon in this planet should be in the form of methane. Theorists are going to be quite busy trying to figure this one out."

The discovery brings astronomers one step closer to probing the atmospheres of distant planets the size of Earth. The methane-free planet, called GJ 436b, is about the size of Neptune, making it the smallest distant planet that any telescope has successfully "tasted," or analyzed. Eventually, a larger space telescope could use the same kind of technique to search smaller, Earth-like worlds for methane and other chemical signs of life, such as water, oxygen and carbon dioxide.

"Ultimately, we want to find biosignatures on a small, rocky world. Oxygen, especially with even a little methane, would tell us that we humans might not be alone," said Stevenson.

"In this case, we expected to find methane not because of the presence of life, but because of the planet's chemistry. This type of planet should have cooked up methane. It's like dipping bread into beaten eggs, frying it, and getting oatmeal in the end," said Joseph Harrington of the University of Central Florida, the principal investigator of the research.

Methane is present on our life-bearing planet, manufactured primarily by microbes living in cows and soaking in waterlogged rice fields. All of the giant planets in our solar system have methane too, despite their lack of cows. Neptune is blue because of this chemical, which absorbs red light. Methane is a common ingredient of relatively cool bodies, including "failed" stars, which are called brown dwarfs.

In fact, any world with the common atmospheric mix of hydrogen, carbon and oxygen, and a temperature up to 1,000 Kelvin (1,340 degrees Fahrenheit) is expected to have a large amount of methane and a small amount of carbon monoxide. The carbon should "prefer" to be in the form of methane at these temperatures.

At 800 Kelvin (or 980 degrees Fahrenheit), GJ 436b is supposed to have abundant methane and little carbon monoxide. Spitzer observations have shown the opposite. The space telescope has captured the planet's light in six infrared wavelengths, showing evidence for carbon monoxide but not methane.

"We're scratching our heads," said Harrington. "But what this does tell us is that there is room for improvement in our models. Now we have actual data on faraway planets that will teach us what's really going on in their atmospheres."

GJ 436b is located 33 light-years away in the constellation Leo, the Lion. It rides in a tight, 2.64-day orbit around its small star, an "M-dwarf" much cooler than our sun. The planet transits, or crosses in front of, its star as viewed from Earth.

Spitzer was able to detect the faint glow of GJ 436b by watching it slip behind its star, an event called a secondary eclipse. As the planet disappears, the total light observed from the star system drops -- this drop is then measured to find the brightness of the planet at various wavelengths. The technique, first pioneered by Spitzer in 2005, has since been used to measure atmospheric components of several Jupiter-sized exoplanets, the so-called "hot Jupiters," and now the Neptune-sized GJ 436b.

"The Spitzer technique is being pushed to smaller, cooler planets more like our Earth than the previously studied hot Jupiters," said Charles Beichman, director of NASA's Exoplanet Science Institute at NASA's Jet Propulsion Laboratory and the California Institute of Technology, both in Pasadena, Calif. "In coming years, we can expect that a space telescope could characterize the atmosphere of a rocky planet a few times the size of the Earth. Such a planet might show signposts of life."

This research was performed before Spitzer ran out of its liquid coolant in May 2009, officially beginning its "warm" mission.

Other authors include: Sarah Nymeyer, William C. Bowman, Ryan A. Hardy and Nate B. Lust from the University of Central Florida; Nikku Madhusudhan and Sara Seager of the Massachusetts Institute of Technology, Cambridge; Drake Deming of NASA's Goddard Space Flight Center, Greenbelt, Md.; and Emily Rauscher of Columbia University, New York.

JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech. Caltech manages JPL for NASA. For more information about Spitzer, visit http://www.spitzer.caltech.edu/spitzer and http://www.nasa.gov/spitzer.

Spitzer Snaps Amazing Photo of Orion Nebula

Scientists at the American space agency have just revealed the latest image they produced of the famous Orion Nebula. The photograph, which was snapped using the NASA Spitzer Space Telescope, one of the four Great Observatories the agency built, shows in great detail the active stellar formation processes taking place in the renowned structure, the team behind the investigation says. In the particular range of infrared wavelengths that Spitzer uses, a large number of hot, young stars have become visible in the new observations, Space reports.

The nebula is located in the “sword” of the Orion constellation (the Hunter). This stellar pattern has been observed since ancient times, researchers say, and many civilizations paid tribute to it. The new NASA image shows the massive amount of stellar gas and dust that permeate the large nebula. Hydrogen gas clouds glow from the massive amount of radiation that blue stars inside it spew out. This is very beneficial for the stellar formation process, as these stellar winds stir and mix the gas and dust, allowing it to accumulate to the concentrations needed to fall in on themselves, and then ignite.

Astronomers plan to use the new datasets to gain more knowledge into why the stars inside the Orion Nebula change and to what extent this process is affected by planetary formation around these celestial bodies. “This is an exploratory project. Nobody has done this before at a wavelength sensitive to the heat from dust circling around so many stars. We are seeing a lot of variation, which may be a result of clumps of warped structures in the planet-forming disks,” says NASA Spitzer Science Center (SSC) principal research investigator, John Stauffer.

The SSC is based in Pasadena, at the California Institute of Technology (Caltech). The image was snapped by Spitzer in May 2009, shortly after it ran out of helium coolant. This forced the team managing the machine to begin a new, “warm” science phase. In this case, the temperature of the telescope is currently at minus 406 degrees Fahrenheit (minus 243 degrees Celsius). The observations session that yielded this new image, just one in 80 others, took 40 days to complete. About 1,500 variable stars have been identified in Orion this far, thanks to Spitzer studies.

Ashes To Ashes Dust To Dust Chandra And Spitzer Have The Gos

A composite image from NASA's Chandra (blue) and Spitzer (green and red-yellow) space telescopes shows the dusty remains of a collapsed star, a supernova remnant called G54.1+0.3. The white source at the center is a dead star called a pulsar, generating a wind of high-energy particles seen by Chandra in blue. The wind expands into the surrounding environment. The infrared shell that surrounds the pulsar wind, seen in red, is made up of gas and dust that condensed out of debris from the supernova explosion. A nearby cluster of stars is being engulfed by the dust. The nature and quantity of dust produced in supernova explosions is a long-standing mystery, and G54.1+0.3 supplies an important piece to the puzzle. Image credit: NASA/CXC/JPL-Caltech/Harvard-Smithsonian CfA

A new image from NASA's Chandra and Spitzer space telescopes shows the dusty remains of a collapsed star. The dust is flying past and engulfing a nearby family of stars.

"Scientists think the stars in the image are part of a stellar cluster in which a supernova exploded," said Tea Temin of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass., who led the study. "The material ejected in the explosion is now blowing past these stars at high velocities."

The composite image of G54.1+0.3 shows the Chandra X-ray Observatory data in blue, and data from the Spitzer Space Telescope in green (shorter wavelength) and red-yellow (longer).

The white source near the center of the image is a dense, rapidly rotating neutron star, or pulsar, left behind after a core-collapse supernova explosion. The pulsar generates a wind of high-energy particles - seen in the Chandra data - that expands into the surrounding environment, illuminating the material ejected in the supernova explosion.

The infrared shell that surrounds the pulsar wind is made up of gas and dust that condensed out of debris from the supernova. As the cold dust expands into the surroundings, it is heated and lit up by the stars in the cluster so that it is observable in infrared.

The dust closest to the stars is the hottest and is seen glowing in yellow in the image. Some of the dust is also being heated by the expanding pulsar wind as it overtakes the material in the shell.

The unique environment into which this supernova exploded makes it possible for astronomers to observe the condensed dust from the supernova that is usually too cold to emit in infrared. Without the presence of the stellar cluster, it would not be possible to observe this dust until it becomes energized and heated by a shock wave from the supernova.

However, the very action of such shock heating would destroy many of the smaller dust particles. In G54.1+0.3, astronomers are observing pristine dust before any such destruction.

G54.1+0.3 provides an exciting opportunity for astronomers to study the freshly formed supernova dust before it becomes altered and destroyed by shocks. The nature and quantity of dust produced in supernova explosions is a long-standing mystery, and G54.1+0.3 supplies an important piece to the puzzle.

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

The Spitzer observations were made before the telescope ran out of its coolant in May 2009 and began its "warm" mission. NASA's Jet Propulsion Laboratory in Pasadena, Calif., manages Spitzer for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.

Spitzer unearths primitive black-holes

These two data plots from Spitzer show a primitive supermassive black hole (top) compared to a typical one. As the data show, the typical supermassive black hole, called J0842+1218, exhibits the signs of a surrounding ring of dust, a feature that appears at longer wavelengths of infrared light. The primitive object, called J0005-0006, lacks a dusty torus.

These Spitzer data, along with other observations not shown here, led to the discovery of the two most primitive supermassive black holes known, J0005-0006 and J0303-0019. Both objects are about 13 billion light-years away.

Usually, a supermassive black hole is surrounded by an accretion disk, which itself is surrounded by a dark doughnut-like dusty structure called a dust torus. But for the primitive black holes, the dust tori are missing and only gas disks are observed. This is because the early universe was clean as a whistle. Enough time had not passed for molecules to clump together into dust particles. Some black holes forming during this era thus started out lacking dust. As they grew, gobbling up more and more mass, they are thought to have accumulated dusty rings.

Credit: NASA/JPL-Caltech/University of Arizona

Astronomers have come across what appear to be two of the earliest and most primitive supermassive black holes known.

The discovery, based largely on observations from NASA's Spitzer Space Telescope, will provide a better understanding of the roots of our universe, and how the very first black holes, galaxies and stars came to be.

"We have found what are likely first-generation quasars, born in a dust-free medium and at the earliest stages of evolution," said Linhua Jiang of the University of Arizona, Tucson. Jiang is the lead author of a paper announcing the findings in the March 18 issue of Nature.

Black holes are beastly distortions of space and time. The most massive and active ones lurk at the cores of galaxies, and are usually surrounded by doughnut-shaped structures of dust and gas that feed and sustain the growing black holes. These hungry, supermassive black holes are called quasars.

As grimy and unkempt as our present-day universe is today, scientists believe the very early universe didn't have any dust -- which tells them that the most primitive quasars should also be dust-free. But nobody had seen such immaculate quasars -- until now. Spitzer has identified two -- the smallest on record -- about 13 billion light-years away from Earth.

The quasars, called J0005-0006 and J0303-0019, were first unveiled in visible light using data from the Sloan Digital Sky Survey. That discovery team, which included Jiang, was led by Xiaohui Fan, a coauthor of the recent paper at the University of Arizona. NASA's Chandra X-ray Observatory had also observed X-rays from one of the objects. X-rays, ultraviolet and optical light stream out from quasars as the gas surrounding them is swallowed.

"Quasars emit an enormous amount of light, making them detectable literally at the edge of the observable universe," said Fan.

When Jiang and his colleagues set out to observe J0005-0006 and J0303-0019 with Spitzer between 2006 and 2009, their targets didn't stand out much from the usual quasar bunch. Spitzer measured infrared light from the objects along with 19 others, all belonging to a class of the most distant quasars known. Each quasar is anchored by a supermassive black hole weighing more than 100 million suns.

Of the 21 quasars, J0005-0006 and J0303-0019 lacked characteristic signatures of hot dust, the Spitzer data showed. Spitzer's infrared sight makes the space telescope ideally suited to detect the warm glow of dust that has been heated by feeding black holes.

"We think these early black holes are forming around the time when the dust was first forming in the universe, less than one billion years after the Big Bang," said Fan. "The primordial universe did not contain any molecules that could coagulate to form dust. The elements necessary for this process were produced and pumped into the universe later by stars."

The astronomers also observed that the amount of hot dust in a quasar goes up with the mass of its black hole. As a black hole grows, dust has more time to materialize around it. The black holes at the cores of J0005-0006 and J0303-0019 have the smallest measured masses known in the early universe, indicating they are particularly young, and at a stage when dust has not yet formed around them.

Other authors include W.N. Brandt of Pennsylvania State University, University Park; Chris L. Carilli of the National Radio Astronomy Observatory, Socorro, N.M.; Eiichi Egami of the University of Arizona; Dean C. Hines of the Space Science Institute, Boulder, Colo.; Jaron D. Kurk of the Max Planck Institute for Extraterrestrial Physics, Germany; Gordon T. Richards of Drexel University, Philadephia, Pa.; Yue Shen of the Harvard Smithsonian Center for Astrophysics, Cambridge, Mass.; Michael A. Strauss of Princeton, N.J.; Marianne Vestergaard of the University of Arizona and Niels Bohr Institute in Denmark; and Fabian Walter of the Max Planck Institute for Astronomy, Germany. Fan and Kurk were based in part at the Max Planck Institute for Astronomy when this research was conducted.

The Spitzer observations were made before the telescope ran out of its liquid coolant in May 2009, beginning its "warm" mission.

Supernova Remnant Is An Unusual Suspect

The main graphic shows the area around SNR 0104 in infrared light from Spitzer (red and green) and X-rays from Chandra (purple). The inset shows a close-up of SNR 0104. (Credit: X-ray: NASA/CXC/PSU/S. Park and J. Lee; IR: NASA/JPL-Caltech)

ScienceDaily (June 14, 2009) — A new image from NASA's Chandra X-ray Observatory shows a supernova remnant with a different look. This object, known as SNR 0104-72.3 (SNR 0104 for short), is in the Small Magellanic Cloud, a small neighboring galaxy to the Milky Way. Astronomers think that SNR 0104 is the remains of a so-called Type Ia supernova caused by the thermonuclear explosion of a white dwarf.

In this composite made of X-rays from Chandra shown in purple and infrared data from Spitzer shown in green and red, SNR 0104 looks unlike other likely Type Ia remnants found in our own Galaxy. While objects such as the Kepler and Tycho supernova remnants appear circular, the shape of SNR 0104 in X-rays is not. Instead, the image is dominated by two bright lobes of emission (seen to the upper right and lower left). The large amount of iron in these lobes indicates that SNR 0104 was likely formed by a Type Ia supernova.

One possible explanation for this structure is that the explosion of the white dwarf itself was strongly asymmetrical and produced two jets of iron. Another possibility is that the complicated environment seen in the image is responsible. The green shells on the left and right side of SNR 0104 correspond to surrounding material that has been swept up by the explosion. So, the unusual shape of the remnant might be caused by a lack of material to the north and south of the star to interrupt the outward path of the stellar debris. This explanation, however, is still in question and scientists hope more data from Chandra and other telescopes will help settle the debate.

The presence of a nearby massive star and the shells of gas and dust seen in the wide-field view from Spitzer shows that SNR 0104 might be located within a star-forming region. This suggests that SNR 0104 may belong to a little-studied class of so-called "prompt" Type Ia supernovas caused by the demise of younger, more massive stars than average. Again, more data will be needed to test this theory.

This research was led by Sangwook Park and Jae-Joon Lee of Penn State University and was presented at the 214th meeting of the American Astronomical Society in Pasadena, California. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

Source: http://www.sciencedaily.com/releases/2009/06/090609130800.htm

Spitzer Catches Star Cooking Up Comet Crystals

For Release: May 13, 2009

Scientists have long wondered how tiny silicate crystals, which need sizzling high temperatures to form, have found their way into frozen comets, born in the deep freeze of the solar system's outer edges. The crystals would have begun as non-crystallized silicate particles, part of the mix of gas and dust from which the solar system developed.

A team of astronomers believes they have found a new explanation for both where and how these crystals may have been created, by using NASA's Spitzer Space Telescope to observe the growing pains of a young, sun-like star. Their study results, which appear in the May 14 issue of Nature, provide new insight into the formation of planets and comets.

The researchers from Germany, Hungary and the Netherlands found that silicate appears to have been transformed into crystalline form by an outburst from a star. They detected the infrared signature of silicate crystals on the disk of dust and gas surrounding the star EX Lupi during one of its frequent flare-ups, or outbursts, seen by Spitzer in April 2008. These crystals were not present in Spitzer's previous observations of the star's disk during one of its quiet periods.

"We believe that we have observed, for the first time, ongoing crystal formation," said one of the paper's authors, Attila Juhasz of the Max-Planck Institute for Astronomy in Heidelberg, Germany. "We think that the crystals were formed by thermal annealing of small particles on the surface layer of the star's inner disk by heat from the outburst. This is a completely new scenario about how this material could be created."

Annealing is a process in which a material is heated to a certain temperature at which some of its bonds break and then re-form, changing the material's physical properties. It is one way that silicate dust can be transformed into crystalline form.

Scientists previously had considered two different possible scenarios in which annealing could create the silicate crystals found in comets and young stars' disks. In one scenario, long exposure to heat from an infant star might anneal some of the silicate dust inside the disk's center. In the other, shock waves induced by a large body within the disk might heat dust grains suddenly to the right temperature to crystallize them, after which the crystals would cool nearly as quickly.

What Juhasz and his colleagues found at EX Lupi didn't fit either of the earlier theories. "We concluded that this is a third way in which silicate crystals may be formed with annealing, one not considered before," said the paper's lead author, Peter Abraham of the Hungarian Academy of Sciences' Konkoly Observatory, Budapest, Hungary.

EX Lupi is a young star, possibly similar to our sun four or five billion years ago. Every few years, it experiences outbursts, or eruptions, that astronomers think are the result of the star gathering up mass that has accumulated in its surrounding disk. These flare-ups vary in intensity, with really big eruptions occurring every 50 years or so.

The researchers observed EX Lupi with Spitzer's infrared spectrograph in April 2008. Although the star was beginning to fade from the peak of a major outburst detected in January, it was still 30 times brighter than when it was quiet. When they compared this new view of the erupting star with Spitzer measurements made in 2005 before the eruption began, they found significant changes.

In 2005, the silicate on the surface of the star's disk appeared to be in the form of amorphous grains of dust. In 2008, the spectrum showed the presence of crystalline silicate on top of amorphous dust. The crystals appear to be forsterite, a material often found in comets and in protoplanetary disks. The crystals also appear hot, evidence that they were created in a high-temperature process, but not by shock heating. If that were the case, they would already be cool.

"At outburst, EX Lupi became about 100 times more luminous," said Juhasz. "Crystals formed in the surface layer of the disk but just at the distance from the star where the temperature was high enough to anneal the silicate--about 1,000 Kelvin (1,340 degrees Fahrenheit)--but still lower than 1,500 Kelvin (2,240 degrees Fahrenheit). Above that, the dust grains will evaporate." The radius of this crystal formation zone, the researchers note, is comparable to that of the terrestrial-planet region in the solar system.

"These observations show, for the first time, the actual production of crystalline silicates like those found in comets and meteorites in our own solar system," said Spitzer Project Scientist Michael Werner of NASA's Jet Propulsion Laboratory, Pasadena, Calif. "So what we see in comets today may have been produced by repeated bursts of energy when the sun was young."

NASA's Spitzer Begins Warm Mission

Artist's concept of Spitzer Space Telescope. Image credit: NASA/JPL-Caltech
› Full image and caption

May 15, 2009

Spitzer Space Telescope Mission Status

PASADENA, Calif. -- After more than five-and-a-half years of probing the cool cosmos, NASA's Spitzer Space Telescope has run out of the coolant that kept its infrared instruments chilled. The telescope will warm up slightly, yet two of its infrared detector arrays will still operate successfully. The new, warm mission will continue to unveil the far, cold and dusty universe.

Spitzer entered standby mode at 3:11 p.m. Pacific Time (6:11 p.m. Eastern Time or 22:11 Universal Time), May 15, as result of running out of its liquid helium coolant. Scientists and engineers will spend the next few weeks recalibrating the instrument at the warmer temperature, and preparing it to begin science operations.

Additional information, including the following items, is at: http://www.nasa.gov/mission_pages/spitzer/news/spitzer-warm.html .
--A full news release about Spitzer's warm mission and past accomplishments
--A mock interview titled "If Spitzer Could Talk: An Interview with NASA's Coolest Space Mission"
--A video about the Spitzer mission
--An article about the late astronomer Lyman Spitzer, the mission's namesake

Detailed information about the Spitzer mission at http://www.spitzer.caltech.edu/spitzer and http://www.nasa.gov/spitzer

Who's Who of the Spitzer mission:
NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer mission for NASA's Science Mission Directorate in Washington, D.C. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Lockheed Martin Space Systems in Denver, and Ball Aerospace & Technologies Corp., in Boulder, Colo., support mission and science operations. NASA's Goddard Space Flight Center in Greenbelt, Md., built Spitzer's infrared array camera; the instrument's principal investigator was Giovanni Fazio of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. Ball Aerospace & Technologies Corp. built Spitzer's infrared spectrograph; its principal investigator was Jim Houck of Cornell University in Ithaca, N.Y. Ball Aerospace & Technologies Corp. and the University of Arizona in Tucson, built the multiband imaging photometer for Spitzer; its principal investigator was George Rieke of the University of Arizona.

Ancient Solar Systems Found Around Dead Stars

Were there once habitable planets long ago around stars that are now dead? A team of astronomers have found evidence that between 1-3 percent of white dwarf stars are orbited by rocky planets and asteroids, suggesting these objects once hosted solar systems similar to our own. White dwarf stars are the compact, hot remnants left behind when stars like our Sun reach the end of their lives. Using data from the Spitzer Space Telescope, an international team of astronomers have determined that asteroids are found in orbit around a large number of white dwarfs, perhaps as many as 5 million in our own Milky Way Galaxy.

The atmospheres of these white dwarf stars should consist entirely of hydrogen and helium but are sometimes found to be contaminated with heavier elements like calcium and magnesium. The new observations suggest that these Earth-sized stars are often polluted by a gradual rain of closely orbiting dust that emits infrared radiation picked up by Spitzer.

Presenting his team’s findings at the European Week of Astronomy and Space Science conference at the University of Hertfordshire, Dr. Jay Farihi of the University of Leicester said that the data from Spitzer suggest that at least 1 in 100 of white dwarf stars are contaminated in this way and that the dust originates from rocky bodies like asteroids (also known as minor planets). In our Solar System, minor planets are the left over building blocks of the rocky terrestrial planets like the Earth.

“In the quest for Earth-like planets, we have now identified numerous systems which are excellent candidates to harbour them,” said Farihi. “Where they persist at white dwarfs, any terrestrial planets will likely not be habitable, but may have been sites where life developed during a previous epoch. “

The new findings indicate the dust is completely contained within the Roche limit of the star — close enough that any object larger than a few kilometers would be ripped apart by gravitational tides (the same phenomenon which led to the creation of Saturn’s rings). This backs up the team’s hypothesis that the dust disks around white dwarfs are produced by tidally disrupted minor planets. In order to pass this close to the white dwarf, an asteroid must be perturbed from its regular orbit further out – and this can occur during a close encounter with as yet unseen planets.

Because white dwarfs descend from main sequence stars like the Sun, the team’s work implies that at least 1% to 3% of main sequence stars have terrestrial planets around them.

Emissions from the White Dwarf System GD 16. Credit: NASA, JPL -Caltech, University of Leicester

Perhaps the most exciting and important aspect of this research is that the composition of these crushed asteroids can be measured using the heavy elements seen in the white dwarf.

Farihi sees this as a crucial step forward. “With high quality optical and ultraviolet observations (e.g. the Hubble Space Telescope), we should be able to measure up to two dozen different elements in debris-polluted white dwarfs. We can then address the question, “Are the rocky extrasolar planets we find similar to the terrestrial planets of our Solar System?”

Source: RAS

Spitzer Catches Star Cooking Up Comet Crystals

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.
› Related animation
Image credit: NASA/JPL-Caltech

May 13, 2009

Scientists have long wondered how tiny silicate crystals, which need sizzling high temperatures to form, have found their way into frozen comets, born in the deep freeze of the solar system's outer edges. The crystals would have begun as non-crystallized silicate particles, part of the mix of gas and dust from which the solar system developed.

A team of astronomers believes they have found a new explanation for both where and how these crystals may have been created, by using NASA's Spitzer Space Telescope to observe the growing pains of a young, sun-like star. Their study results, which appear in the May 14 issue of Nature, provide new insight into the formation of planets and comets.

The researchers from Germany, Hungary and the Netherlands found that silicate appears to have been transformed into crystalline form by an outburst from a star. They detected the infrared signature of silicate crystals on the disk of dust and gas surrounding the star EX Lupi during one of its frequent flare-ups, or outbursts, seen by Spitzer in April 2008. These crystals were not present in Spitzer's previous observations of the star's disk during one of its quiet periods.

"We believe that we have observed, for the first time, ongoing crystal formation," said one of the paper's authors, Attila Juhasz of the Max-Planck Institute for Astronomy in Heidelberg, Germany. "We think that the crystals were formed by thermal annealing of small particles on the surface layer of the star's inner disk by heat from the outburst. This is a completely new scenario about how this material could be created."

Annealing is a process in which a material is heated to a certain temperature at which some of its bonds break and then re-form, changing the material's physical properties. It is one way that silicate dust can be transformed into crystalline form.

Scientists previously had considered two different possible scenarios in which annealing could create the silicate crystals found in comets and young stars' disks. In one scenario, long exposure to heat from an infant star might anneal some of the silicate dust inside the disk's center. In the other, shock waves induced by a large body within the disk might heat dust grains suddenly to the right temperature to crystallize them, after which the crystals would cool nearly as quickly.

What Juhasz and his colleagues found at EX Lupi didn't fit either of the earlier theories. "We concluded that this is a third way in which silicate crystals may be formed with annealing, one not considered before," said the paper's lead author, Peter Abraham of the Hungarian Academy of Sciences' Konkoly Observatory, Budapest, Hungary.

EX Lupi is a young star, possibly similar to our sun four or five billion years ago. Every few years, it experiences outbursts, or eruptions, that astronomers think are the result of the star gathering up mass that has accumulated in its surrounding disk. These flare-ups vary in intensity, with really big eruptions occurring every 50 years or so.

The researchers observed EX Lupi with Spitzer's infrared spectrograph in April 2008. Although the star was beginning to fade from the peak of a major outburst detected in January, it was still 30 times brighter than when it was quiet. When they compared this new view of the erupting star with Spitzer measurements made in 2005 before the eruption began, they found significant changes.

In 2005, the silicate on the surface of the star's disk appeared to be in the form of amorphous grains of dust. In 2008, the spectrum showed the presence of crystalline silicate on top of amorphous dust. The crystals appear to be forsterite, a material often found in comets and in protoplanetary disks. The crystals also appear hot, evidence that they were created in a high-temperature process, but not by shock heating. If that were the case, they would already be cool.

"At outburst, EX Lupi became about 100 times more luminous," said Juhasz. "Crystals formed in the surface layer of the disk but just at the distance from the star where the temperature was high enough to anneal the silicate--about 1,000 Kelvin (1,340 degrees Fahrenheit)--but still lower than 1,500 Kelvin (2,240 degrees Fahrenheit). Above that, the dust grains will evaporate." The radius of this crystal formation zone, the researchers note, is comparable to that of the terrestrial-planet region in the solar system.

"These observations show, for the first time, the actual production of crystalline silicates like those found in comets and meteorites in our own solar system," said Spitzer Project Scientist Michael Werner of NASA's Jet Propulsion Laboratory, Pasadena, Calif. "So what we see in comets today may have been produced by repeated bursts of energy when the sun was young."

JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.

More information about Spitzer is at http://www.spitzer.caltech.edu/spitzer and http://www.nasa.gov/spitzer

If Spitzer Could Talk: An Interview with NASA's Coolest Space Telescope

May 04, 2009

NASA's Spitzer Space Telescope is about to use its last drop of the coolant that has chilled it for the past five-and-a-half years. On about May 12, give or take a week or so, the observatory is predicted to run out of the liquid helium that has run through its veins, keeping its infrared detectors at frosty operating temperatures of just a few degrees above the coldest temperature possible, called absolute zero.

The spacecraft, which is now in orbit around the sun more than 100-million kilometers (62-million miles) behind Earth, will heat up just a bit -- its instruments will warm up from - 456 degrees Fahrenheit (-271 Celsius) to - 404 degrees Fahrenheit (-242 Celsius). This is still way colder than an ice cube, which is about 32 degrees Fahrenheit. More importantly, it is still cold enough for some of Spitzer's infrared detectors to keep on probing the cosmos for at least two more years.

If Spitzer could talk, here's how an interview with the observatory might go:

Interviewer: It's cold in here.

Spitzer: Sorry. Even though I'm warming up, I still need to be quite chilly for two of my infrared channels to continue working.

Interviewer: Why do infrared telescopes need to be cold?

Spitzer: Good question. Infrared light is produced by heat. So, engineers reduce my own heat to make sure that I'm measuring just the infrared light from the objects I'm studying. This is the same reason why I circle around the sun, far behind Earth, and why I have big sun shields -- to keep cool.

Interviewer: Tell me, Spitzer, about what you consider to be your greatest discovery?

Spitzer: Probably my work on exoplanets, which are planets that orbit stars other than our sun. I hate to brag, but I was the first telescope to see actual light from an exoplanet. I was also the first to split that light up into a spectrum. Oh, sorry, there I go again with the techie talk. Light is made up of lots of different wavelengths in the same way that a rainbow is made up of different colors. I was able to split an exoplanet's light up into its various infrared wavelengths. This spectral information teaches us about planets' atmospheres.

Interviewer: What did you learn about the planets?

Spitzer: For one thing, I learned that the hot gas exoplanets, called "hot Jupiters," are not all alike. Some are wild, with temperatures as hot as fire and almost as cold as ice. Others are more even-keeled. I also created the first temperature map of an exoplanet, and watched a storm of colossal proportions brewing across the face of one bizarre exoplanet – it has an orbit that swings in really close to its star and then back out to about where Earth sits in our solar system.

Interviewer: You seem to really like planets.

Spitzer: Well, you know, I wasn't even originally designed to see exoplanets! It was a complete surprise to me that I had this amazing ability. I can tell you that I do, and always will, have a thing for planetary disks. Because I have infrared eyes, I can see the warm and dusty planetary materials that swirl in disks around young stars. I can also see older disks littered with the remnants of planets. In fact, I've probably looked at thousands of disks so far. What's been fun is finding them around all sorts of oddball stars, such as those that are dead, doubled up as twins and even as small as planets. Bottom line is that the process of growing planets seems to happen quite easily all over the galaxy, and perhaps the universe.

Interviewer: Does that mean aliens could be everywhere?

Spitzer: I can't really give you a good answer for that. Yes, the studies of disks are showing us that rocky planets are common, but we don't know if the planets could have life. Also, keep in mind that, as of now, nobody has detected any planets that are just like Earth. These would be rocky worlds around stars like our sun that have the right temperature for lakes and oceans. That job will most likely fall to NASA's Kepler mission, which will begin hunting for them soon.

Interviewer: Did you look at other objects besides disks and planets?

Spitzer: Oh yes, certainly. I have looked at comets in our solar system, the farthest galaxies known, and everything in-between. I was really excited to find hundreds of hidden black holes billions of light-years away. Astronomers had known they were there because they shoot X-rays into space that can be detected as a diffuse glow. But the objects themselves were choked in dust. My infrared eyes, unlike your human eyes, can see through dust, so I was able to round up a lot of these missing black holes.

Interviewer: Is there any other discovery you want to mention?

Spitzer: There are too many to list, but I am particularly proud of this huge mosaic I took of a large swath of our Milky Way galaxy. It looks stunning when you print it out to poster size, and it's the best view ever of the bustling central portion of our galaxy. You see, the middle of the Milky Way is hopping with stars and dust. It's chaos, and visible-light cannot escape. These observations not only look cool, they also helped astronomers remap the structure of our galaxy. The new map shows just two spiral arms of stars instead of four as previously believed. How crazy is that!

Interviewer: So what lies ahead?

Spitzer: Well, I'm really looking forward to the warm mission, because now that I have just two infrared channels working, I have more time to look at larger chunks of space for longer periods of time. I can help astronomers answer some really important "big picture" questions, which we didn't have time for before.

Interviewer: Can you list some specific projects you'll be working on?

Spitzer: I plan to continue studying exoplanets, including new "hot Jupiters" that Kepler is expected to find. I will also refine estimates of the rate at which our local universe, or space, is expanding. And I will stare at the very distant universe, trying to see some of the farthest objects possible. Oh, and I am also going to survey thousands of asteroids in our neck of the solar system, and get the first real estimate of their size distribution. This will tell us approximately how often big asteroids might come close to Earth.

Interviewer: That sounds scary.

Spitzer: Actually, this information will help us prepare for them. And NASA tracks near-Earth objects diligently. More information can only help.

Interviewer: Will you still take the pretty pictures?

Spitzer: You think my pictures are pretty? Thank you! Yes, I will still snap a lot of pictures. For instance, I will continue to probe cloudy star-forming regions in our galaxy, which often make dramatic pictures.

Interviewer: Anything else you'd like to add?

Spitzer: My cool years have been more than I could ask for, and I look forward to more adventures to come. I'd also like to thank all of the scientists and engineers who have worked so hard to make my mission an ongoing success. And, if any of my fans out there want more info, they can go to www.spitzer.caltech.edu/spitzer.