April 20, 2005

Dolores Beasley
Headquarters, Washington 
(Phone: 202/358-1753) 

Whitney Clavin <br > Jet Propulsion Laboratory, Pasadena, Calif.
(Phone: 818/354-4673) 

RELEASE: 05-101

NASA'S SPITZER TELESCOPE SEES SIGNS OF 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, California Institute of Technology 
(Caltech), 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," 
he added.

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 the star's 
rubble.

One of NASA's future planet-hunting missions, SIM PlanetQuest, may 
ultimately identify such a planet orbiting this star. 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 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. 

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 Caltech. 

For artist's concepts and more information related to this release on 
the Internet, visit: 

http://www.spitzer.caltech.edu/spitzer 

For information about NASA and agency programs on the Internet, visit: 


http://www.nasa.gov 

	
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