[meteorite-list] UCLA Astronomers Identify Evidence of Asteroid Belt Around Nearby Star

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:44:11 2004
Message-ID: <200106041908.MAA16853_at_zagami.jpl.nasa.gov>

http://www.astro.ucla.edu/~cchen/hr1998_pr.html

FOR RELEASE: 9:20 a.m. PDT, June 4, 2001

UCLA Astronomers Identify Evidence of Asteroid Belt Around Nearby Star;
Findings Indicate Potential for Planet or Asteroid Formation

Identifying what may be a galactic replay of how our own solar system was
formed, UCLA astronomers have found evidence of a massive asteroid belt
around a nearby star-- findings that could indicate that planets are forming
there or have already formed.

The observations, reported today at the annual meeting of the American
Astronomical Society by UCLA graduate student Christine Chen and her
advisor, Michael Jura, reveal that a star identified as zeta Leporis (HR
1998) is enveloped by swirling dust in quantities and at temperatures that
indicate a massive asteroid belt could surround the star.

"Because of the conditions we identified near zeta Lep, we believe that the
dust around this star may contain asteroids that appear to be colliding
violently with each other," said Jura, a professor in UCLA's Department of
Physics and Astronomy. "zeta Lep is a relatively young star-- approximately
the age of our Sun when the Earth was forming. The system we observed around
zeta Lep is similar to what we think occurred in the early years when
planets and asteroids were created."

zeta Lep is located in the constellation Lepus (the Hare) about 70 light
years from our sun. About twice as massive as our sun, zeta Lep is young in
astronomical terms-- about 100 million years old, compared to our Sun, which
is about 4.5 billion years old.

"Our current findings may be just the tip of the iceberg of what we may
ultimately learn about the objects surrounding zeta Lep," said Chen.

"In simplest terms, our planets formed when smaller objects smashed
together," she said. "Dust that surrounds a star will eventually either fall
into the star, or collide with itself and create bigger particles. The
particles we can identify around zeta Lep may be forming chunks of rock or
larger objects; asteroids or even planets may be forming or have already
formed around zeta Lep."

Orbiting dust around hydrogen-burning stars such as Vega, beta Pictoris and
zeta Lep was first discovered in 1983 with the Infrared Astronomy Satellite
(IRAS). The orbiting dust absorbs optical light from the central star and is
emitted as infrared. The presence of this dust around zeta Lep indicates
that material similar to that found in our own Solar System surrounds this
star.

In February, Chen and Jura observed zeta Lep with Long Wavelength
Spectrometer, an infrared camera on the 10-meter telescope at the Keck
Observatory on Mauna Kea, Hawaii. Chen and Jura found infrared-emitting dust
confined to a region smaller than 12.2 Astronomical Units in diameter, a
region similar in size is similar-- in astronomical scales-- to the asteroid
belt in our Solar System, which is about 5.4 Astronomical Units in diameter.

                              [Image] [Image]

By observing at two infrared wavelengths, Chen and Jura estimate that the
average temperature of the dust around zeta Lep is about 340 Kelvins (150
F), a relatively high temperature for such material. Given this high
temperature, the grains may be as close as 2.5 Astronomical Units to the
star.

"There must be objects larger than dust around zeta Lep, which may resemble
asteroids in our own Solar System, that are creating the infrared-emitting
dust by violently colliding with each other," said Jura.

The discovery that the dust around zeta Lep is unusually warm was first
published in 1991 by astronomers Hartmut Aumann and Ronald Probst.

Chen and Jura plan to confirm their findings with infrared observations of
zeta Lep with additional infrared observations.

We hope to obtain infrared spectra of the emission from zeta Lep," Chen
said. "We want to know if the asteroids around this star are similar in
composition to objects in our Solar System, and we want to learn if the
processes we now see unfolding on zeta Lep can help us understand how the
planets in our own Solar System formed."

"The next step is to get an infrared spectrum of this area, which would give
us an indication of their composition."

The research by Chen and Jura is supported by funding from NASA.

For More Information:

Ms. Christine Chen (310-825-3172, cchen_at_astro.ucla.edu)
Professor Michael Jura (310-825-4302, jura_at_astro.ucla.edu)
Received on Mon 04 Jun 2001 03:08:41 PM PDT