[meteorite-list] Dust Green and the Five Dwarfs

From: Darren Garrison <cynapse_at_meteoritecentral.com>
Date: Sun Oct 23 23:38:46 2005
Message-ID: <03mol15vnlfof81ljgbn57loof83mtrchh_at_4ax.com>

http://www.msnbc.msn.com/id/9772274/

Planetary seeds spotted around brown dwarfs
Spitzer telescope detects ingredients needed to create a planet

By Robert Roy Britt
Space.com
Updated: 6:58 p.m. ET Oct. 21, 2005


PASADENA, Calif. - Some potential stars just don't quite make it. They don't have enough mass to
trigger the thermonuclear fusion that powers regular stars. They stall out, more massive than a
planet but not as hot as a star.

Astronomers call these failed stars brown dwarfs. Theory suggests planets could form around them.
One such setup has been found but not confirmed.

Now NASA's Spitzer Space Telescope has found what may be the first stages of planet formation around
brown dwarfs.

Small clumps of microscopic dust grains and tiny crystals were detected orbiting five brown dwarfs.
The material has flattened into a thin disk, which is what astronomers believe occurs before planets
form around regular stars like the sun.

The material in the newfound disks is the very stuff of planet formation, according to leading
theory. It is the same ingredients spotted around regular young stars in other studies.

The recipe has also been found in comets, which astronomers believe to be relatively pristine
leftovers of the planet-formation process in our solar system.

"We are learning that the first stages of planet formation are more robust than previously
believed," said D?niel Apai, an astronomer at the University of Arizona and member of the NASA
Astrobiology Institute.

The results are detailed in today's issue of the journal Science.

Strange worlds
A brown dwarf shines in the infrared but releases very little if any visible light. Brown dwarfs
have also been found orbiting other stars and orbiting other brown dwarfs.

The brown dwarfs in the study are all about 520 light-years away, in the Chamaeleon constellation.
They range in mass from 40 to 70 times the heft of Jupiter. They are young, at roughly 1 million to
3 million years old. Our Sun is 4.6 billion years old.

Planets around brown dwarfs would be dark and cold, so astronomers don't know if life could form on
them.

Analysis of the Spitzer data shows that the dust particles have crystallized and are sticking
together. One key ingredient found was the mineral olivine, the researchers said.

"We are seeing processed particles that are linking up and growing in size," said Ilaria Pascucci,
also from the University of Arizona and a co-author of the study. "This is exciting because we
weren't sure if the disks of such cool objects would behave the same way that stellar disks do."

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Received on Sun 23 Oct 2005 11:47:11 PM PDT