[meteorite-list] NASA's Spitzer Telescope Sees Signs of Alien Asteroid Belt

[Ron Baalke]

Dolores Beasley
Headquarters, Washington              April 20, 2005
(Phone: 202/358-1753)

Whitney Clavin
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: 

www.spitzer.caltech.edu/spitzer

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

http://www.nasa.gov

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