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

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed Apr 20 14:08:56 2005
Message-ID: <200504201808.j3KI8QC25772_at_zagami.jpl.nasa.gov>

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

-end-
Received on Wed 20 Apr 2005 02:08:25 PM PDT