[meteorite-list] NASA's Spitzer Finds Possible Comet Dust Around Dead Star

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed Jan 11 12:55:20 2006
Message-ID: <200601111753.k0BHrgV14228_at_zagami.jpl.nasa.gov>

Jan. 11, 2006

Erica Hupp/George Deutsch
Headquarters, Washington
(202) 358-1237/1324

RELEASE: 06-009

NASA'S SPITZER FINDS POSSIBLE COMET DUST AROUND DEAD STAR

NASA's Spitzer Space Telescope spotted what may be comet dust
sprinkled around the white dwarf star G29-38 that died approximately
500 million years ago.

The findings suggest the star, which most likely consumed its inner
planets, is still orbited by a ring of surviving comets and possibly
outer planets. This is the first observational evidence that comets
can outlive their suns.

"Astronomers have known for decades that stars are born, have an
extended middle age, and then wither away or explode. Spitzer is
helping us understand how planetary systems evolve in tandem with
their parent stars," said David Leisawitz, NASA's Spitzer program
scientist.

Astronomers believe white dwarfs are shrunken skeletons of stars that
were once similar to Earth's sun. As the stars aged over billions of
years, they grew brighter and eventually swelled in size to become
red giants. Millions of years later, the red giants shed their outer
atmospheres, leaving behind white dwarfs.

If any planets orbited in these systems, the red giants would have
engulfed at least the inner ones. Only distant outer planets and an
orbiting icy outpost of comets would have survived.

"The dust seen by Spitzer around G29-38 was probably generated
relatively recently when one such outlying comet may have been
knocked into the inner region of the system and ripped into dust
shreds by the tidal forces of the star," said astronomer William
Reach of the Spitzer Science Center at the California Institute of
Technology (Caltech) in Pasadena, Calif.

Prior to the Spitzer findings, astronomers studying G29-38 noticed an
unusual and unknown source of infrared light. Spitzer, with its
powerful infrared spectrometer, was able to break this light apart
revealing its molecular makeup. These data told astronomers the light
was coming from the same types of dusty minerals found in comets in
our solar system.

"We detected a large quantity of very small, dirty silicate grains,"
said astronomer Marc Kuchner of NASA's Goddard Space Flight Center,
Greenbelt, Md. "The size of these grains tells us they are probably
from comets and not other planetary bodies."

In our own solar system, comets reside in the cold outer fringes in
regions known as the Kuiper Belt and Oort Cloud. Only when something
disturbs their orbits, such as another comet or an outer planet, do
they begin periodic journeys into the sun's warmer neighborhood.
However, these trips to the tropics often end in destruction. Comets
slowly disintegrate as they pass close to the sun or they crash into
it. They also occasionally crash into planets, as comet
Shoemaker-Levy 9 did when it plunged into Jupiter.

Though the dust seen by Spitzer around the white dwarf is most likely
the remains of such a torn-up comet, there may be other explanations.
One possibility is a second wave of planets formed long after the
death of the star, leaving a dusty construction zone.

Kuchner presented his findings today at the 207th meeting of the
American Astronomical Society in Washington. The findings were
published in the December 20, 2005, issue of the Astrophysical
Journal.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the
Spitzer Space Telescope mission for the agency's Science Mission
Directorate. Science operations are conducted at the Spitzer Science
Center at Caltech. JPL is a division of Caltech.

For artists' concepts, other graphics and more information about
Spitzer on the Web, visit:

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

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

http://www.nasa.gov/home/

-end-
Received on Wed 11 Jan 2006 12:53:41 PM PST