[meteorite-list] Evidence of Extrasolar Asteroid Belt

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 8 Jan 2007 09:34:51 -0800 (PST)
Message-ID: <200701081734.JAA22680_at_zagami.jpl.nasa.gov>

http://www.sciencenews.org/articles/20070106/fob5.asp

Rocky Finding: Evidence of extrasolar asteroid belt
Ron Cowen
Science News
January 6, 2007

Astronomers report that they've obtained the best evidence yet for an
asteroid belt beyond the solar system. Such a belt would suggest that
the star Zeta Leporis, which lies just 70 light-years away, possesses
not only asteroids but rocky planets like Earth.

The new measurements pinpoint the location of a disk of warm dust that
surrounds Zeta Leporis. The dust lies about the same distance from the
star as the solar system's asteroid belt lies from the sun, Margaret M.
Moerchen and Charles M. Telesco of the University of Florida in
Gainesville and their colleagues report in an upcoming Astrophysical
Journal Letters.

Most previously observed disks have been cool and lie much farther from
their parent stars, in the region that corresponds in the solar system
to the locale of Pluto and the reservoir of comets known as the Kuiper
belt.

The close-in dust around Zeta Leporis probably arose when several
asteroids bumped into each other, grinding rock into a fine spray of
particles, or when a large asteroid, perhaps 100 kilometers in diameter,
suffered a cataclysmic wallop, Moerchen and Telesco say.

"The [precise] measurement of the Zeta Leporis disk is a very exciting
result," says Charles Beichman of NASA's Jet Propulsion Laboratory in
Pasadena, Calif. "We now have direct evidence for structures around
other stars that are directly analogous to the asteroid belt in our
solar system."

Zeta Leporis entered the limelight in the 1980s, when a satellite
revealed that the star and its surroundings emitted much more infrared
light than was expected from the star alone. That's a sign that dust
swaddles Zeta Leporis.

In 2001, Christine Chen and Michael Jura of the University of
California, Los Angeles observed the star with one of the telescopes at
the Keck Observatory on Hawaii's Mauna Kea. They found that the dust is
probably confined to a disk with a radius no larger than 6.1
astronomical units (AU) - slightly greater than Jupiter's distance from
the sun (SN: 6/16/01, p. 375:
http://www.sciencenews.org/articles/20010616/fob8.asp).

In February 2005, the team led by Moerchen and Telesco viewed Zeta
Leporis with the Gemini South telescope atop Cerro Pachon in Chile.
Those observations for the first time enabled researchers to precisely
gauge the size of the dust disk.

The team finds that most of the dust is concentrated at a distance of 3
AU from Zeta Leporis. That's similar to the location of the solar
system's asteroid belt, which stretches between 2.1 and 3.3 AU from the
sun.

Because asteroids are leftovers from the planet-making process in the
solar system, the new study "supports the thought that Earthlike planets
may exist" outside the solar system, says Jura. Compared with our sun,
Zeta Leporis is a youngster, but it's still old enough to have formed
planets.

Moerchen's team is planning further observations to reveal the Zeta
Leporis disk's shape. If it's circular and uniform in density, the disk
probably formed by the slow grinding of asteroids over thousands of
years. A more distorted shape would suggest that the dust was generated
by a collision between two large chunks of rock only about 100 years
ago, Telesco says.

"For years we've been studying Kuiper belt - like disks; now, we're
investigating the architecture of the inner asteroidal regions" around
stars. "This is kind of new territory," Telesco says.
Received on Mon 08 Jan 2007 12:34:51 PM PST