[Spitzer News] Closest Planetary System Hosts Two Asteroid Belts

spitzer-news at lists.ipac.caltech.edu spitzer-news at lists.ipac.caltech.edu
Mon Oct 27 10:27:50 PDT 2008


Announcement
1) Spitzer Nominated for 2008 Podcast Award

Press Releases
1) Closest Planetary System Hosts Two Asteroid Belts  (27 October 2008)
2) NASA's Spitzer Gets Sneak Peek Inside Comet Holmes  (13 October 2008)
3) Splashy Portrait Helps Explain How Stars Form  (08 October 2008)

Features
1) Massive Young Stars Trigger Stellar Birth (October 07, 2008)
2) Artists and Astronomers 'Observe' the Universe Together (October 07, 2008)


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=  Announcement  =
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1)Spitzer Nominated for 2008 Podcast Award

Spitzer's "IRrelevant Astronomy" video series has been nominated for a 2008
Podcast Award, in the Technology/Science category. It is one of only two
astronomy-themed podcasts to be nominated, and the only one produced by a
NASA mission.

If you enjoy this podcast, please consider taking a moment to vote for us.

"IRrelevant Astronomy" uses CG animation and comedy to bring astronomy news
& science to a general audience in a fun way. Entertainment website
Aint-It-Cool-News has reviewed it as "the most (intentionally) hilarious
series of educational films you'll find...the pieces carry a Muppets-esque
charm."

Every IP address/e-mail address can vote once every 24 hours between now and
November 6th.

Vote for the 2008 Podcast Awards:
http://www.podcastawards.com/
(The Technology/Science category is at the bottom of the page)

IRrelevant Astronomy home page:
http://www.coolcosmos.ipac.caltech.edu/videos/irrelevant


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= Press Releases =
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1) Closest Planetary System Hosts Two Asteroid Belts  (27 October 2008)
http://www.spitzer.caltech.edu/Media/releases/ssc2008-19/release.shtml

New observations from NASA's Spitzer Space Telescope indicate that the nearest planetary system to our own has two asteroid belts. Our own solar system has just one.

The star at the center of the nearby system, called Epsilon Eridani, is a younger, slightly cooler and fainter version of the sun. Previously, astronomers had uncovered evidence for two possible 
planets in the system, and for a broad, outer ring of icy comets similar to our own Kuiper Belt.

Now, Spitzer has discovered that the system also has dual asteroid belts. One sits at approximately the same position as the one in our solar system. The second, denser belt, most likely also 
populated by asteroids, lies between the first belt and the comet ring. The presence of the asteroid belts implies additional planets in the Epsilon Eridani system.

"This system probably looks a lot like ours did when life first took root on Earth," said Dana Backman, an astronomer at the SETI Institute, in Mountain View, Calif., and outreach director for NASA's 
Sofia mission. "The main difference we know of so far is that it has an additional ring of leftover planet construction material." Backman is lead author of a paper about the findings to appear Jan. 
10 in the Astrophysical Journal.

Asteroid belts are rocky and metallic debris left over from the early stages of planet formation. Their presence around other stars signals that rocky planets like Earth could be orbiting in the 
system's inner regions, with massive gas planets circling near the belts' rims. In our own solar system, for example, there is evidence that Jupiter, which lies just beyond our asteroid belt, caused 
the asteroid belt to form long ago by stirring up material that would have otherwise coalesced into a planet. Nowadays, Jupiter helps keep our asteroid belt confined to a ring.

Astronomers have detected stars with signs of multiple belts of material before, but Epsilon Eridani is closer to Earth and more like our sun overall. It is 10 light-years away, slightly less massive 
than the sun, and roughly 800 million years old, or one-fifth the age of the sun.

Because the star is so close and similar to the sun, it is a popular locale in science fiction. The television series Star Trek and Babylon 5 referenced Epsilon Eridani, and it has been featured in 
novels by Issac Asimov and Frank Herbert, among others.

The popular star was also one of the first to be searched for signs of advanced alien civilizations using radio telescopes in 1960. At that time, astronomers did not know of the star's young age.

Spitzer observed Epsilon Eridani with both of its infrared cameras and its infrared spectrometer. When asteroid and comets collide or evaporate, they release tiny particles of dust that give off heat, 
which Spitzer can see. "Because the system is so close to us, Spitzer can really pick out details in the dust, giving us a good look at the system's architecture," said co-author Karl Stapelfeldt of 
NASA's Jet Propulsion Laboratory, Pasadena, Calif.

The asteroid belts detected by Spitzer orbit at distances of approximately 3 and 20 astronomical units from the star (an astronomical unit is the average distance between Earth and the sun). For 
reference, our own asteroid belt lies at about 3 astronomical units from the sun, and Uranus is roughly 19 astronomical units away.

One of the two possible planets previously identified around Epsilon Eridani, called Epsilon Eridani, was discovered in 2000. The planet is thought to orbit at an average distance of 3.4 astronomical 
units from the star -- just outside the innermost asteroid belt identified by Spitzer. This is the first time that an asteroid belt and a planet beyond our solar system have been found in a similar 
arrangement as our asteroid belt and Jupiter.

Some researchers had reported that Epsilon Eridani b orbits in an exaggerated ellipse ranging between 1 and 5 astronomical units, but this means the planet would cross, and quickly disrupt, the 
newfound asteroid belt. Instead, Backman and colleagues argue that this planet must have a more circular orbit that keeps it just outside the belt.

The other candidate planet was first proposed in 1998 to explain lumpiness observed in the star's outer comet ring. It is thought to lie near the inner edge of the ring, which orbits between 35 and 90 
astronomical units from Epsilon Eridani.

The intermediate belt detected by Spitzer suggests that a third planet could be responsible for creating and shepherding its material. This planet would orbit at approximately 20 astronomical units 
and lie between the other two planets. "Detailed studies of the dust belts in other planetary systems are telling us a great deal about their complex structure," said Michael Werner, co-author of the 
study and project scientist for Spitzer at JPL. "It seems that no two planetary systems are alike."

These results were presented this week at the "New Light on Young Stars: Spitzer's View of Circumstellar Disks" conference in Pasadena, Calif.
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2) NASA's Spitzer Gets Sneak Peek Inside Comet Holmes  (13 October 2008)
http://www.spitzer.caltech.edu/Media/releases/ssc2008-18/release.shtml

When comet Holmes unexpectedly erupted in 2007, professional and amateur astronomers around the world turned their telescopes toward the spectacular event. Their quest was to find out why the comet 
had suddenly exploded.

Observations taken of the comet after the explosion by NASA's Spitzer Space Telescope deepen the mystery, showing oddly behaving streamers in the shell of dust surrounding the nucleus of the comet. 
The data also offer a rare look at the material liberated from within the nucleus, and confirm previous findings from NASA's Stardust and Deep Impact missions.

"The data we got from Spitzer do not look like anything we typically see when looking at comets," said Bill Reach of NASA's Spitzer Science Center at the California Institute of Technology, Pasadena, 
Calif. Reach is lead investigator of the Spitzer observations. "The comet Holmes explosion gave us a rare glimpse at the inside of a comet nucleus." The findings were presented at the 40th meeting of 
the Division of Planetary Sciences in Ithaca, N.Y.

Every six years, comet 17P/Holmes speeds away from Jupiter and heads inward toward the sun, traveling the same route typically without incident. However, twice in the last 116 years, in November 1892 
and October 2007, comet Holmes exploded as it approached the asteroid belt, and brightened a millionfold overnight.

In an attempt to understand these odd occurrences, astronomers pointed NASA's Spitzer Space Telescope at the comet in November 2007 and March 2008. By using Spitzer's infrared spectrograph instrument, 
Reach was able to gain valuable insights into the composition of Holmes' solid interior. Like a prism spreading visible-light into a rainbow, the spectrograph breaks up infrared light from the comet 
into its component parts, revealing the fingerprints of various chemicals.

In November of 2007, Reach noticed a lot of fine silicate dust, or crystallized grains smaller than sand, like crushed gems. He noted that this particular observation revealed materials similar to 
those seen around other comets where grains have been treated violently, including NASA's Deep Impact mission, which smashed a projectile into comet Tempel 1; NASA's Stardust mission, which swept 
particles from comet Wild 2 into a collector at 13,000 miles per hour (21,000 kilometers per hour), and the outburst of comet Hale-Bopp in 1995.

"Comet dust is very sensitive, meaning that the grains are very easily destroyed, said Reach. "We think the fine silicates are produced in these violent events by the destruction of larger particles 
originating inside the comet nucleus."

When Spitzer observed the same portion of the comet again in March 2008, the fine-grained silicate dust was gone and only larger particles were present. "The March observation tells us that there is a 
very small window for studying composition of comet dust after a violent event like comet Holmes' outburst," said Reach.

Comet Holmes not only has unusual dusty components, it also does not look like a typical comet. According to Jeremie Vaubaillon, a colleague of Reach's at Caltech, pictures snapped from the ground 
shortly after the outburst revealed streamers in the shell of dust surrounding the comet. Scientists suspect they were produced after the explosion by fragments escaping the comet's nucleus.

In November 2007, the streamers pointed away from the sun, which seemed natural because scientists believed that radiation from the sun was pushing these fragments straight back. However, when Spitzer 
imaged the same streamers in March 2008, they were surprised to find them still pointing in the same direction as five months before, even though the comet had moved and sunlight was arriving from a 
different location. "We have never seen anything like this in a comet before. The extended shape still needs to be fully understood," said Vaubaillon.

He notes that the shell surrounding the comet also acts peculiarly. The shape of the shell did not change as expected from November 2007 to March 2008. Vaubaillon said this is because the dust grains 
seen in March 2008 are relatively large, approximately one millimeter in size, and thus harder to move.

"If the shell was comprised of smaller dust grains, it would have changed as the orientation of the sun changes with time," said Vaubaillon. "This Spitzer image is very unique. No other telescope has 
seen comet Holmes in this much detail, five months after the explosion."

"Like people, all comets are a little different. We've been studying comets for hundreds of years -- 116 years in the case of comet Holmes -- but still do not really understand them," said Reach. 
"However, with the Spitzer observations and data from other telescopes, we are getting closer."
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3)Splashy Portrait Helps Explain How Stars Form  (08 October 2008)
http://www.spitzer.caltech.edu/Media/releases/ssc2008-17/release.shtml

Different wavelengths of light swirl together like watercolors in a new, ethereal portrait of a bright, star-forming region.

The multi-wavelength picture combines infrared, visible and X-ray light from NASA's Spitzer Space Telescope, the European Southern Observatory's New Technology Telescope, and the European Space 
Agency's XMM-Newton orbiting X-Ray telescope, respectively.

The colorful image offers a fresh look at the history of the star-studded region, called NGC 346, revealing new information about how stars form in the universe. NGC 346 is the brightest star-forming 
region in the Small Magellanic Cloud, a so-called irregular dwarf galaxy that orbits our Milky Way galaxy, 210,000 light-years away.

"NGC 346 is an astronomical zoo," said Dimitrios Gouliermis of the Max Planck Institute for Astronomy in Germany, lead author of a new paper describing the observations in an upcoming issue of the 
Astrophysical Journal. "When we combined data at various wavelengths, we were able to tease apart what's going on in different parts of the cloud."

Small stars are scattered throughout the NGC 346 region, while massive stars populate its center. The massive stars and most of the small stars formed at the same time out of one dense cloud, while 
other small stars were created later through a process called triggered star formation. Intense radiation from massive stars ate away at the surrounding dusty cloud, triggering gas to expand and 
create shock waves that compressed nearby cold dust and gas into new stars. The red-orange filaments surrounding the center of the image show where this process has occurred.

But a set of even younger small stars in the region, seen as a pinkish blob at the top of the image, couldn't be explained by this mechanism. Scientists were scratching their heads over what caused 
this seemingly isolated group of stars to form.

By combining multi-wavelength data of NGC 346, Gouliermis says he and his team were able to pinpoint the trigger as a very massive star that blasted apart in a supernova explosion about 50,000 years 
ago. According to the astronomers, this very massive star spurred the isolated young stars into existence before it died, but through a different type of triggered star formation than that which 
occurred near the center of the region. Fierce winds from the massive star, and not radiation, pushed dust and gas together, compressing it into new stars.

The finding demonstrates that both wind- and radiation-induced triggered star formation are at play in the same cloud. According to Gouliermis, "The result shows us that star formation is a far more 
complicated process than we used to believe, comprising different competitive or collaborative mechanisms."

The new image also reveals a bubble, seen as a blue halo to the left, caused by the supernova explosion that happened 50,000 years ago. Further analysis shows that this bubble is located within a 
large expanding gaseous shell, possibly powered by the explosion and the winds of other bright stars in its vicinity.

Infrared light (red) shows cold dust; visible light (green) denotes glowing gas; and X-rays (blue) represent very warm gas. Ordinary stars appear as blue spots with white centers, while young stars 
enshrouded in dust appear as red spots with white centers.

Other authors of this paper include Thomas Henning and Wolfgang Brandner of the Max Planck Institute for Astronomy, and You-Hua Chu and Robert Gruendl of the University of Illinois at Urbana-Champaign.

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==== Features ====
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1) Massive Young Stars Trigger Stellar Birth (October 07, 2008)
http://www.spitzer.caltech.edu/Media/happenings/20081007a

RCW 108 is a region where stars are actively forming within the Milky Way galaxy about 4,000 light years from Earth. This is a complicated region that contains young star clusters, including one that 
is deeply embedded in a cloud of molecular hydrogen. By using data from different telescopes, astronomers determined that star birth in this region is being triggered by the effect of nearby, massive 
young stars.

This image is a composite of X-ray data from NASA's Chandra X-ray Observatory (blue) and infrared emission detected by NASA's Spitzer Space Telescope (red and orange). More than 400 X-ray sources were 
identified in Chandra's observations of RCW 108. About 90 percent of these X-ray sources are thought to be part of the cluster and not stars that lie in the field-of-view either behind or in front of 
it. Many of the stars in RCW 108 are experiencing the violent flaring seen in other young star-forming regions such as the Orion nebula. Gas and dust blocks much of the X-rays from the juvenile stars 
located in the center of the image, explaining the relative dearth of Chandra sources in this part of the image.

The Spitzer data show the location of the embedded star cluster, which appears as the bright knot of red and orange just to the left of the center of the image. Some stars from a larger cluster, known 
as NGC 6193, are also visible on the left side of the image. Astronomers think that the dense clouds within RCW 108 are in the process of being destroyed by intense radiation emanating from hot and 
massive stars in NGC 6193.

Taken together, the Chandra and Spitzer data indicate that there are more massive star candidates than expected in several areas of this image. This suggests that pockets within RCW 108 underwent 
localized episodes of star formation. Scientists predict that this type of star formation is triggered by the effects of radiation from bright, massive stars such as those in NGC 6193. This radiation 
may cause the interior of gas clouds in RCW 108 to be compressed, leading to gravitational collapse and the formation of new stars.
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2) Artists and Astronomers 'Observe' the Universe Together (October 07, 2008)
http://www.spitzer.caltech.edu/Media/happenings/20081007

Our current view of the universe, to quote Albert Einstein, is "not weirder than we do imagine, but weirder than we can imagine." That said, we have no choice but to observe the universe through human 
eyes and brains. How can we even start to make sense of it?

One answer might be to call in the artists. For thousands of years, people have used art to explore ideas that humble, confuse or even frighten us. A new exhibition opening in Pasadena continues this 
tradition, bringing artists and astronomers together to create original pieces of art.

Called "Observe," the exhibition is the culmination of a yearlong collaboration between two Pasadena institutions -- the Art Center College of Design and NASA's Spitzer Science Center at the 
California Institute of Technology. Beginning Oct. 10, visitors to the Art Center's Williamson Gallery will be challenged to stretch their imaginations as infrared observations from NASA's Spitzer 
Space Telescope are visualized through the minds of five contemporary Southern California artists.

"Science is bringing us spectacular discoveries that torque our everyday perception of reality. Things like black holes, multiple universes and time distortions challenge our human-centered culture 
and beliefs," said Stephen Nowlin, director of the Williamson Gallery. "This is an exhibition about the newly unknown."

Dan Goods, an Observe artist and a visual strategist at NASA's Jet Propulsion Laboratory in Pasadena, was fascinated by the idea that light from distant stars and galaxies travels for years before 
reaching us. "Some of those stars died thousands of years ago, and they only exist in the light that is still on its way to our eyes," he pointed out.

Goods built a clock that spans a large room. Spheres throughout the room represent the hours. The spheres all look the same at the entrance, but like stars in the sky, they are actually different 
sizes and distances away. Speakers on the spheres play back sounds from people in the room, distorted and delayed by random time increments. This distortion represents a phenomenon called "redshift" 
in astronomy, in which light is stretched to longer wavelengths as it travels through space. "It's like the stars are talking to you," Goods explained.

Other projects include an interactive video installation by Daniel Wheeler, which invites visitors to "send" data all over the world to create an abstract collage of images; and a planetarium-like 
room filled with changing projections of the stars by Lita Albuquerque. George Legrady used a projected laser to make patterns representing all the pointing commands that have been sent up to Spitzer 
in space. And Lynn Aldrich created a fake-fur wormhole -- a theoretical tunnel through space and time -- that people can crawl through.

"I was amazed by the serendipities that cropped up," said Michelle Thaller, outreach manager at the Spitzer Science Center. "Lynn Aldrich's furry wormhole is a great way to represent the weird, almost 
chaotic nature of other dimensions!"

"I've always thought that Spitzer's images were spectacular, but working with the artists has made me look at scientific data in a whole new way," she added. "Data out of context can become art."

Observe opens to the public on Oct. 10 as part of ArtNight Pasadena, a weekend of art around town sponsored by the Pasadena Arts and Culture Commission. Opening-night hours are 6 to 10 p.m. The 
exhibition will run though Jan. 9, 2009, ushering in the International Year of Astronomy, a yearlong celebration of the 400th anniversary of Galileo and the first telescope.

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