Posted on by Fraser Cain

Aureum Chaos Region on Mars

This image, taken by the High Resolution Stereo Camera (HRSC) on board ESA?s Mars Express spacecraft, shows the ‘chaotic’ terrain of the Aureum Chaos region on Mars.

The HRSC obtained this image during orbit 456 with a resolution of approximately 25 metres per pixel. The scene shows an area located at about 3? South and 335? East.

Aureum Chaos is located in the eastern part of Valles Marineris, south-west of the 280 kilometre-wide impact crater Aram Chaos. Like this impact basin, both regions are two examples of the chaotic terrain contained in this part of the Valles Marineris.

As the name ?chaos? suggests, this terrain is characterised by randomly oriented, large-scale mesas and knobs that are heavily eroded and dominate the area. As seen in the main colour image, these mesas range from a few kilometres to tens of kilometres wide.

In the north (right-hand side) of this image, a well-defined scarp extends in an east-west direction.

?Slump and collapse? blocks can be distinguished at the base of this scarp, as highlighted in this close-up perspective view.

Near the southern border (middle left-hand side) of the colour image, a roughly five kilometre-wide region of bright material is observed. This material appears to form distinct layers that may have been created by the evaporation of fluids or by hydrothermal activity (see lower right-hand corner of the perspective view below).

Another interesting region of bright material also extends north to south in the centre of the colour image and is also visible along the left side of this perspective view.

The history of Aureum Chaos is complex. It appears that this basin was filled with sediment and then experienced the formation of chaotic terrain. It is thought that this extremely rough terrain is caused by collapse of the surface due to the removal of subsurface ice, magma or water.

By supplying new image data for Aureum Chaos, the HRSC allows scientists to improve their understanding of Mars. In particular, the colour and stereo capability of the HRSC allows improved studies of the planet?s morphology (the evolution of rocks and landforms). By analysing reflected light at different wavelengths, we can determine minerals that make up the various geological features within the scene.

Data from the HRSC, coupled with information from the other instruments on ESA?s Mars Express and other missions, will provide new insights into the geological evolution of the Red Planet and also pave the way for future missions.

Original Source: ESA News Release

Posted on by Fraser Cain

Shuttle Return Pushed Back a Week

Mission controllers have decided to give technicians an extra week to get the Space Shuttle Discovery ready for its return to flight. Originally schedule to lift off on May 15, Discovery is now tentatively set to return to orbit on May 22. One reason for the delay is to give technicians more time to test an extension to the Canadarm which will let astronauts examine the shuttle for damage while in orbit. Its launch window closes on June 3, and doesn’t open up again until mid-July when Atlantis is expected to launch.

Posted on by Fraser Cain

Glimpse at the Envelope of a Young Star

Detailed new images of the starbirth nursery in the Omega Nebula (M17) have revealed a multi component structure in the envelope of dust and gas surrounding a very young star. The stellar newborn, called M17-SO1, has a flaring torus of gas and dust, and thin conical shells of material above and below the torus. Shigeyuki Sako from University of Tokyo and a team of astronomers from the National Astronomical Observatory of Japan, the Japan Aeorospace Exploration Agency, Ibaraki University, the Purple Mountain Observatory of the Chinese Academy of Sciences, and Chiba University obtained these images and analyzed them in infrared wavelengths in order to understand the mechanics of protoplanetary disk formation around young stars. Their work is described in a detailed article in the April 21, 2005 edition of Nature.

The research team wanted to find a young star located in front of a bright background nebula and use near-infrared observations to image the surrounding envelope in silhouette, in a way comparable to how dentists use X-rays to take images of teeth. Using the Infrared Camera and Spectrograph with Adaptive Optics on the Subaru telescope, the astronomers looked for candidates in and around the Omega Nebula, which lies about 5,000 light-years away in the constellation Sagittarius. They found a large butterfly-shaped near-infrared silhouette of an envelope about 150 times the size of our solar system surrounding a very young star. They made follow-up observations of the region using the Cooled Mid-Infrared Camera and Spectrograph on the Subaru telescope and the Nobeyama Millimeter Array at the Nobeyama Radio Observatory. By combining the results from the near-infrared, mid-infrared, and millimeter wave radio observations, the researchers determined that the M17-SO1 is a protostar about 2.5 to 8 times the mass of the Sun, and that the butterfly-like silhouette reveals an edge-on view of the envelope.

The near-infrared observations reveal the structure of the surrounding envelope with unprecedented levels of detail. In particular, observations using the 2.166 emission line of hydrogen (called the Brackett gamma (Br ?) line) show that the envelope has multiple components instead of one simple structure. Around the equator of the protostar, the torus of dust and gas increases in thickness farther way from the star. Thin cone-shaped shells of material extend away from both poles of the star.

The discovery of the multi-component structure puts new constraints on how an envelope feeds material to a protostellar disk forming within its boundaries. “It’s quite likely that our own solar system looked like M17-SO1 when it was beginning to form,” said Sako. “We hope to confirm the relevance of our discovery for understanding the mechanism of protoplanetary disk formation by using the Subaru telescope to take infrared images with high resolution and high sensitivity of many more young stars.?

Original Source: NOAJ News Release

Posted on by Fraser Cain

Genesis Recovery Proceeding Well

Scientists have closely examined four Genesis spacecraft collectors, vital to the mission’s top science objective, and found them in excellent shape, despite the spacecraft’s hard landing last year.

Scientists at NASA’s Johnson Space Center (JSC) in Houston removed the four solar-wind collectors from an instrument called the concentrator. The concentrator targets collected solar-oxygen ions during the Genesis mission. Scientists will analyze them to measure solar-oxygen isotopic composition, the highest-priority measurement objective for Genesis. The data may hold clues to increase understanding about how the solar system formed.

“Taking these concentrator targets out of their flight holders and getting our first visual inspection of them is very important,” said Karen McNamara, Genesis curation recovery lead. “This step is critical to moving forward with the primary science Genesis was intended to achieve. All indications are the targets are in excellent condition. Now we will have the opportunity to show that quantitatively. The preliminary assessment of these materials is the first step to their allocation and measurement of the composition of the solar wind,” she said.

The targets were removed at JSC by a team from Los Alamos National Laboratory, Los Alamos, N.M., where the concentrator was designed and built.

“Finding these concentrator targets in excellent condition after the Genesis crash was a real miracle,” said Roger Wiens, principal investigator for the Los Alamos instruments. “It raised our spirits a huge amount the day after the impact. With the removal of the concentrator targets this week, we are getting closer to learning what these targets will tell us about the sun and our solar system,” he added.

The Los Alamos team was assisted by JSC curators and Quality Assurance personnel from NASA’s Jet Propulsion Laboratory in Pasadena, Calif. Curators at JSC will examine the targets and prepare a detailed report about their condition, so scientists can properly analyze the collectors. The targets will be imaged in detail and then stored under nitrogen in the Genesis clean room.

Genesis was launched Aug. 8, 2001, from Cape Canaveral Air Force Station, Fla., on a mission to collect solar wind particles. Sample collection began Dec. 5, 2001, and was completed April 1, 2004. After an extensive recovery effort, following its Sept. 8, 2004, impact at a Utah landing site, the first scientific samples from Genesis arrived at JSC Oct. 4, 2004.

Original Source: NASA News Release

Posted on by Fraser Cain

Audio: Alpha, Still Constant After All These Years

Image credit: SDSS
Listen to the interview: Alpha, Still Constant After All These Years (3.3 MB)

Or subscribe to the Podcast: universetoday.com/audio.xml

Fraser Cain: Can you give me the primer on Alpha?

Jeffery Newman: So Alpha is one of the constants that describes the strength of a fundamental force; there are 4 fundamental forces: electromagnetism, the weak force, the strong force and gravity and Alpha basically determines the strength of the electromagnetic force compared to the other 4. As such, it’s a very basic part of the quantum theory of how these forces work and how they scale with energy (and) how they scale with time in the universe.

Fraser: What in the universe depends on it; how would the universe be different if Alpha was different?

Newman: Because Alpha determines how strong the electromagnetic force is; that’s the force that holds atoms together; that’s the force that causes things to interact with light, so if the force (Alpha) had different strength, atoms wouldn’t hold together, as well or they might hold together too strongly to allow chemical interactions. As well, if light and atoms didn’t interact very well, it would be very hard to see for instance, as we do. It is essential to our life. Because it’s so fundamental, it has ramifications all over the place that you wouldn’t even expect that can have affects on almost every interaction an atom undergoes or how an atom is structured.

Fraser: Where did the prediction come from that Alpha should remain constant since the Big Bang? Why was this even open to speculation?

Newman: It was generally expected that it was a universal constant of the universe. There were predictions in fact, that it was not just a constant, but a very simple constant that would be an integer; whatever 136 or whatever 137. For a while it was thought to be the value; not a 137.1, but a 137 even. That turned out to be numerology; it didn’t hold true, but it’s a value that comes out of nowhere, but is a fundamental part of the standard model of particle physics and all the other standard values of particle physics are things like the mass of an electron, the very basic thing. We would expect that there would be numbers that would describe the universe as a whole and if they describe the universe as a whole, they should describe they should describe it at any time or any place. Only in the last 20 or so years, when there have been unification theories, that predict many extra dimensions; there are theories that also predict that the constants of the universe as we perceive them are influenced by the presence of these extra dimensions and over time or over space, the values of these constants could actually change because of the extra degrees of freedom provided by these dimensions. Dark energy theories today also can predict changes in Alpha over time.

Fraser: Now I had reported a week before your story had come out that some Australian researchers had found that Alpha had been changing which I guess was a pretty big announcement. Do you know what research they had done to determine that it had changed?

Newman: So they’re using ? again an astrophysical method; trying to look at observations of very distant objects, deep in the past; in the distant universe, and tried to use those observations to look at quantities that should depend on Alpha; in their case, they’re looking at the wavelengths of light that are absorbed by gasses between us and quasars that are very bright objects, very far away. They have a method that tried to use many different kinds of elements counterbalancing each other trying to get as much sensitivity to Alpha as possible, but because it’s a complicated method, it requires a lot of complicated calculations. It’s certainly a more complicated method than the one we’ve tried. We’ve tried to keep things simple. So there are actually some groups who have used the same method and some of them have found changes in Alpha and some of them have found no change in Alpha with the method the Australian group is using.

Fraser: What was the method that you had used?

Newman: We are looking, not at quasars, not at the very brightest objects, but rather at galaxies which are more abundant. So we can look at greater numbers of objects. And it turns out that we are looking at a particular simple set of measurements, set of wavelengths; transitions in atoms that we can use to measure Alpha. It depends in a very straightforward way on the value of Alpha over time, so by making a pretty simple measurement, we were able to set a constraint on how Alpha could evolve without having to worry about lots of atomic physics and nuclear physics, but just the simplest thing we can do. Alpha is called the Fine Structure Constant, and we were actually measuring the strength of a Fine Structure transition in oxygen atoms.

Fraser: How precise is the calculations that you’re coming up with?

Newman: The precision is mostly limited by the just the number of objects we have in the DEEPTWO Redshift Survey; the dataset we’ve used to do this. Now, out of 50,000 objects in the survey, we have about 500 we can use for this test. That gives us a precision of about a part in 30,000 on the value of Alpha.

Fraser: Because I recall the Australians, it (Alpha) had changed in 1 in 100,000 or something like that?

Newman: Yes, so we can’t yet rule out their measurement. It’s modestly discrepant at this point. No scientist would look at these values and say one rules out the other because their nominal precision is high. The question is could there be something systematically wrong with the measurement; could there be something that goes wrong with that technique? Given that different groups have gotten different values it’s likely that something is wrong with one of the groups or the other; either the group that defines a change in Alpha or the group that doesn’t. We can’t yet rule that out, but with a larger sample, using our simple method, we can make a determination.

Fraser: What would it take then for you to be able to come to a conclusive answer that both you; the changers and the static people come to an agreement?

Newman: I think that more data coming from us would certainly help because currently we are able to show that we are not limited by any sort of systematic error or systematic uncertainty in what we’re doing. We are limited just by random errors and random errors, you can make better if you have a larger sample. The other techniques, the other groups are also trying to get more data to reduce their errors and to try to do measurements of a couple of different types to see if they can get consistent answers, not just with this more complex version of the method of looking at quasars, but now they are taking a step back and trying to use a slightly simpler method of that as well. So, hopefully these will converge and try to come to a common answer once their data sets come in.

Fraser: Right. Let’s say that you are wrong and it (Alpha) has been changing over time, what could that mean for the future of the universe? If it keeps going.

Newman: So the changes that are found are relatively slow; even the groups that do find significant changes and the changes that are found would be expected to get slower and slower as time goes on. Most predictions are that if Alpha does change, that it’s mostly changing in the first seconds of the universe. It just gets slower and slower and slower after that. So a secondary effect in the end, if it’s very slowly changing, the stars will burn out before it changes enough to affect the chemistry and interactions of atoms.

Posted on by Fraser Cain

Penumbral Lunar Eclipse, April 24

Image credit: NASA
NASA is planning to send people back to the Moon. Target date: 2015 or so. Too bad they won’t be there this Sunday because, on April 24th, there’s going to be a solar eclipse, and you can only see it from the Moon.

On Earth, solar eclipses happen when the Moon covers the Sun. On the Moon, the roles are reversed. It’s Earth that covers the Sun. Such an eclipse is “a marvelous sight,” according to Apollo 12 astronaut Alan Bean, who saw one in 1969. He was flying home from the Moon along with crewmates Pete Conrad and Dick Gordon when their spaceship flew through Earth’s shadow. “Our home planet [eclipsed] our own star.”

No one will see the April 24th eclipse, but we can imagine what it would be like:

You’re standing on the Moon. It’s broad daylight, almost high noon. The Sun is creeping slowly across the sky. How slowly? A lunar day is about 29.5 Earth-days long. So the Sun moves 29.5 times slower than our Earth-sense tells us it should. At that leisurely pace, the Sun approaches a dark but faintly-glowing disk three times its own size.

The disk is Earth with its nightside facing the Moon. You can see moonlit clouds floating over Earth’s dark oceans and continents. You can also see a faintly glowing ring of light around the planet–that’s Earth’s atmosphere with sunlight trickling through it. A telescope would show you Earth’s city lights, too. Beautiful.

Then the eclipse begins.

Looking through dark-filtered glasses, you watch the Sun slip behind Earth. Earth’s atmosphere, lit from behind, glows red, then redder, a ring of fire the color of sunset, interrupted here and there by the tops of the highest clouds.

Ninety minutes later–patience is required!–only a little bit of the Sun remains poking out over the edge of the planet. Arranged just so, the pair remind you of a giant sparkling diamond ring.

The Sun never completely vanishes because this eclipse is partial, not total. During a total eclipse, Earth would hide the Sun completely, which has the odd effect of turning the Moon blood red. But that’s another story.

Partial eclipses, while not as eerie or dramatic as total eclipses, are still good. In fact, future space tourists will probably rocket to the Moon to see them. It’ll be an exclusive club, people who’ve witnessed Earth taking a bite out of the Sun. The membership in 2005 is only two: Alan Bean and Dick Gordon, the surviving crew of Apollo 12.

Stuck on Earth, what can you do? As a matter of fact, it is possible to observe this Sunday’s solar eclipse from Earth in a roundabout way:

During the eclipse, Earth’s shadow will fall across the Moon and we can see that happen. Our planet’s shadow has two parts, a dark inner core called the umbra and a pale outer fringe called the penumbra. (Aside: Step outside on a sunny day and look at your own shadow. It’s dark in the middle and pale-fuzzy around the edges. You have your own umbra and penumbra.) The Moon on April 24th will glide through Earth’s penumbra, producing what astronomers call a “penumbral lunar eclipse.”

Penumbral eclipses are not easy to see because the penumbra is so pale. If you’re enthusiastic about such things, however, it’s worth a look. A subtle but distinct shading should be visible across northern parts of the Moon during greatest eclipse around 09:55 UT on Sunday morning, April 24th. That’s 02:55 a.m. PDT or 05:55 a.m. EDT in North America. The best place to be is the Hawaiian Islands where the eclipse happens only 5 minutes before local midnight on Saturday, April 23rd. The Moon will be high in the sky, ideally placed.

Even in Hawaii the experience is subtle. Not impressed? You’re just on the wrong world.

Original Source: Science@NASA

Posted on by Fraser Cain

Solar Nebula Lasted 2 Million Years

Image credit: William K. Hartmann/PSI
The oxygen and magnesium content of some of the oldest objects in the universe are giving clues to the lifetime of the solar nebula, the mass of dust and gas that eventually led to the formation of our solar system.
Specimen from the Allende Meteorite

By looking at the content of chondrules and calcium aluminum-rich inclusions (CAIs), both components of the primitive meteorite Allende, Lab physicist Ian Hutcheon, with colleagues from the University of Hawaii at Manoa, the Tokyo Institute of Technology and the Smithsonian Institution, found that the age difference between the two fragments points directly to the lifetime of the solar nebula.

CAIs were formed in an oxygen-rich environment and date to 4.567 billion years old, while chondrules were formed in an oxygen setting much like that on Earth and date to 4.565 billion, or less, years old.

?Over this span of about two million years, the oxygen in the solar nebula changed substantially in its isotopic makeup,? Hutcheon said. ?This is telling us that oxygen was evolving fairly rapidly.?

The research appears in the April 21 edition of the journal Nature.

One of the signatures of CAIs is an enrichment of the isotope Oxygen 16 (O-16). An isotope is a variation of an element that is heavier or lighter than the standard form of the element because each atom has more or fewer neutrons in its nucleus. The CAIs in this study are enriched with an amount of O-16 4 percent more than that found on Earth. And, while 4 percent may not sound like much, this O-16 enrichment is an indelible signature of the oldest solar system objects, like CAIs. CAIs and chondrules are tens of millions of years older than more modern objects in the solar system, such as planets, which formed about 4.5 billion years ago.

?By the time chondrules formed, the O-16 content changed to resemble what we have on Earth today,? Hutcheon said.

In the past, the estimated lifetime of the solar nebula ranged from less than a million years to ten million years. However, through analysis of the mineral composition and oxygen and magnesium isotope content of CAIs and chondrules, the team was able to refine that lifespan to roughly two million years.

?In the past the age difference between CAIs and chondrules was not well-defined,? Hutcheon said. ?Refining the lifetime of the solar nebula is quite significant in terms of understanding how our solar system formed.?

Founded in 1952, Lawrence Livermore National Laboratory has a mission to ensure national security and apply science and technology to the important issues of our time. Lawrence Livermore National Laboratory is managed by the University of California for the U.S. Department of Energy’s National Nuclear Security Administration.

Original Source: LLNL News Release

Posted on by Fraser Cain

Extreme Life in Yellowstone Gives More Hope for Life on Mars

University of Colorado at Boulder researchers say a bizarre group of microbes found living inside rocks in an inhospitable geothermal environment at Wyoming’s Yellowstone National Park could provide tantalizing clues about ancient life on Earth and help steer the hunt for evidence of life on Mars.

The CU-Boulder research team reported the microbes were discovered in the pores of rocks in a highly acidic environment with high concentrations of metals and silicates at roughly 95 degrees F in Yellowstone’s Norris Geyser Basin. The new study shows the microbe communities are subject to fossilization and have the potential to become preserved in the geologic record.

Scientists believe similar kinds of geothermal environments may once have existed on Mars, where astrobiologists have intensified the search for past and present life forms in recent years.

A paper by CU-Boulder doctoral student Jeffrey Walker, postdoctoral fellow John Spear and Professor Norman Pace of CU-Boulder’s molecular, cellular and developmental biology department and the Center for Astrobiology appears in the April 21 issue of Nature.

The research was funded by the National Science Foundation and NASA.

“This is the first description of these microbial communities, which may be a good diagnostic indicator of past life on Mars because of their potential for fossil preservation,” said Walker. “The prevalence of this type of microbial life in Yellowstone means that Martian rocks associated with former hydrothermal systems may be the best hope for finding evidence of past life there.”

Located about 20 miles northwest of Yellowstone Lake, Norris Geyser Basin is considered to be the hottest and most active geyser basin in Yellowstone and perhaps the world. It also is extremely acidic, according to the researchers.

“The pores in the rocks where these creatures live has a pH value of one, which dissolves nails,” said Pace. “This is another example that life can be robust in an environment most humans view as inhospitable.”

The process used to identify the organisms developed by Pace is much more sensitive than standard lab-culturing techniques that typically yield a small, biased fraction of organisms from any environment, said Walker. In this method, the researchers detected and identified organisms by reading gene sequences.

“Each kind of organism has a unique sequence, which is used to map its position in the tree of life,” said Walker. “It’s a family tree of sorts that describes the genetic relationship between all known organisms.”

Walker discovered the new microbe community in 2003 after breaking apart a chunk of sandstone-like rock in the Norris Geyser Basin. “I immediately noticed a distinctive green band just beneath the surface,” he said. “It was one of those ‘eureka’ moments.”

An analysis determined the green band was caused by a new species of photosynthetic microbes in the Cyanidium group, a kind of alga that is among the most acid-tolerant photosynthetic organisms known, said Walker. Cyanidium organisms made up about 26 percent of the microbes identified in the Norris Geyser Basin study by the CU-Boulder team, Walker said.

Surprisingly, the most abundant microbes identified by the team were a new species of Mycobacterium, a group of microbes best known for causing human illnesses like tuberculosis and leprosy, Walker said. Extremely rare and never before identified in such extreme hydrothermal environments, Mycobacterium made up 37 percent of the total number of microbes identified by the CU-Boulder team.

Pace described the new life form in the Norris Geyser Basin as “pretty weird.” “It may well be a new type of lichen-like symbiosis,” said Pace, who won a MacArthur Fellowship, or “genius grant,” in 2001. “It resembles a lichen, but instead of being comprised of a symbiosis between a fungus and an alga, it seems to be an association of the Mycobacterium with an alga.”

While photosynthesis appears to be a key energy source for most of the creatures, at least some Yellowstone microbes are believed to get energy from the dissolved metals and hydrogen found in the pore water of the rock, Walker said. A study by the CU-Boulder team published by the National Academy of Sciences in January 2005 indicated Yellowstone microbe populations living in hot springs at temperatures more than 158 degrees F use hydrogen as their primary fuel source.

The research effort in the Norris Geyser Basin shows that rock formation processes occurring in the hydrothermal environment under study make very real fossil imprints of the organisms embedded in the rock at various stages, showing how the distinctive fossils develop over time, according to the research team.

“Remnants of these communities could serve as ‘biosignatures’ and provide important clues about ancient life associated with geothermal environments on Earth or elsewhere in the Solar System,” the authors wrote in Nature.

Original Source: University of Colorado News Release

Posted on by Fraser Cain

Podcast: Alpha, Still Constant After All These Years

There’s a number in the Universe which we humans call alpha – or the fine structure constant. It shows up in almost every mathematical formula dealing with magnetism and electricity. The very speed of light depends on it. If the value for alpha was even a little bit different, the Universe as we know it wouldn’t exist – you, me and everyone on Earth wouldn’t be here. Some physicists have recently reported that the value for alpha has been slowly changing since the Big Bang. Others, including Jeffrey Newman from the Lawrence Berkeley National Laboratory have good evidence that alpha has remained unchanged for at least 7 billion years.
Continue reading “Podcast: Alpha, Still Constant After All These Years”

Posted on by Fraser Cain

Spitzer Sees an Alien Asteroid Belt

NASA’s Spitzer Space Telescope has spotted what may be the dusty spray of asteroids banging together in a belt that orbits a star like our Sun. The discovery offers astronomers a rare glimpse at a distant star system that resembles our home, and may represent a significant step toward learning if and where other Earths form.

“Asteroids are the leftover building blocks of rocky planets like Earth,” said Dr. Charles Beichman of the California Institute of Technology, Pasadena, Calif. Beichman is lead author of a paper that will appear in the Astrophysical Journal. “We can’t directly see other terrestrial planets, but now we can study their dusty fossils.”

Asteroid belts are the junkyards of planetary systems. They are littered with the rocky scraps of failed planets, which occasionally crash into each other, kicking up plumes of dust. In our own solar system, asteroids have collided with Earth, the moon and other planets.

If confirmed, the new asteroid belt would be the first detected around a star about the same age and size as our Sun. The star, called HD69830, is located 41 light-years away from Earth. There are two other known distant asteroid belts, but they circle younger, more massive stars.

While this new belt is the closest known match to our own, it is not a perfect twin. It is thicker than our asteroid belt, with 25 times as much material. If our solar system had a belt this dense, its dust would light up the night skies as a brilliant band.

The alien belt is also much closer to its star. Our asteroid belt lies between the orbits of Mars and Jupiter, whereas this one is located inside an orbit equivalent to that of Venus.

Yet, the two belts may have one important trait in common. In our solar system, Jupiter acts as an outer wall to the asteroid belt, shepherding its debris into a series of bands. Similarly, an unseen planet the size of Saturn or smaller may be marshalling this star’s rubble.

One of NASA’s future planet-hunting missions, SIM PlanetQuest, may ultimately identify such a planet orbiting HD 69830. The mission, which will detect planets as small as a few Earth masses, is scheduled to launch in 2011.

Beichman and colleagues used Spitzer’s infrared spectrograph to observe 85 Sun-like stars. Only HD 69830 was found to possibly host an asteroid belt. They did not see the asteroids themselves, but detected a thick disk of warm dust confined to the inner portion of the star system. The dust most likely came from an asteroid belt in which dusty smash-ups occur relatively frequently, about every 1,000 years.

“Because this belt has more asteroids than ours, collisions are larger and more frequent, which is why Spitzer could detect the belt,” said Dr. George Rieke, University of Arizona, Tucson, co-author of the paper. “Our present-day solar system is a quieter place, with impacts of the scale that killed the dinosaurs occurring only every 100 million years or so.”

To confirm that the dust detected by Spitzer is indeed ground-up asteroids, a second less-likely theory will have to be ruled out. According to the astronomers, it is possible a giant comet, almost as big as Pluto, got knocked into the inner solar system and is slowly boiling away, leaving a trail of dust. This hypothesis came about when the astronomers discovered the dust around the star consists of small silicate crystals like those found in comet Hale-Bopp. One of these crystals is the bright green-colored gem called forsterite.

“The ‘super comet’ theory is more of a long shot,” Beichman said, “but we’ll know soon enough.” Future observations of the star using Spitzer and ground-based telescopes are expected to conclude whether asteroids or comets are the source of the dust.

Other authors of this study include G. Bryden, T. Gautier, K. Stapelfeldt and M. Werner of NASA’s Jet Propulsion Laboratory, Pasadena, Calif.; and K. Misselt, J. Stansberry and D. Trilling of the University of Arizona.

The Jet Propulsion Laboratory 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. Spitzer’s infrared spectrograph was built by Cornell University, Ithaca, N.Y. Its development was led by Dr. Jim Houck of Cornell.

For artist’s concepts and more information, visit: www.spitzer.caltech.edu/spitzer.

Original Source: Spitzer News Release