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| |  | | | | NASA's Spitzer Finds Failed Stars May Succeed in Planet Business
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10.20.05
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NASA's Spitzer Space Telescope has spotted the very beginnings
of what might become planets around the puniest of celestial orbs
- brown dwarfs, or "failed stars."
 Image right: This artist's concept shows microscopic crystals in the dusty disk surrounding a brown dwarf, or "failed star." The crystals, made up of a green mineral found on Earth called olivine, are thought to help seed the formation of planets.
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The telescope's infrared eyes have for the first time detected
clumps of microscopic dust grains and tiny crystals orbiting five
brown dwarfs. These clumps and crystals are thought to collide and
further lump together to eventually make planets. Similar materials
are seen in planet-forming regions around stars and in comets, the
remnants of our own solar system's construction.
The findings provide evidence that brown dwarfs, despite being colder
and dimmer than stars, undergo the same initial steps of the
planet-building process.
"We are learning that the first stages of planet formation are more
robust than previously believed," said Dr. Daniel Apai, an astronomer
at the University of Arizona, Tucson, and member of the NASA Astrobiology
Institute's Life and Planets Astrobiology Center. "Spitzer has given us
the possibility to study how planets are built in widely different environments."
The observations also imply that brown dwarfs might be good targets for future
planet-hunting missions. Astronomers do not know if life could exist on planets
around brown dwarfs.
Brown dwarfs differ from stars largely due to their mass. They lack the mass
to ignite internally and shine brightly. However, they are believed to arise
like stars, out of thick clouds of gas and dust that collapse under their own
weight. And like stars, brown dwarfs develop disks of gas and dust that circle
around them. Spitzer has observed many of these disks, which glow at infrared
wavelengths.
Apai and his team used Spitzer to collect detailed information on the minerals
that make up the dust disks of six young brown dwarfs located 520 light-years
away, in the Chamaeleon constellation. The six objects range in mass from about
40 to 70 times that of Jupiter, and they are roughly 1 to 3 million years old.
The astronomers discovered that five of the six disks contain dust particles that
have crystallized and are sticking together in what may be the early phases of
planet assembling. They found relatively large grains and many small crystals of
a mineral called olivine.
"We are seeing processed particles that are linking up and growing in size," said
Dr. Ilaria Pascucci, a co-author also of the University of Arizona. "This is
exciting because we weren't sure if the disks of such cool objects would behave
the same way that stellar disks do."
The team also noticed a flattening of the brown dwarfs' disks, which is another
sign that dust is gathering up into planets.
A paper on these findings appears online today in Science. Authors of the paper
also include Drs. Jeroen Bouwman, Thomas Henning and Cornelis P. Dullemond of
the Max Planck Institute for Astronomy, Germany; and Dr. Antonella Natta of the
Osservatorio Astrofisico di Arcetri, Italy.
NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer mission
for NASA's Science Mission Directorate. Science operations are conducted at the
Spitzer Science Center at the California Institute of Technology in Pasadena.
Spitzer's infrared spectrograph, which made the observations, was built by Cornell
University, Ithaca, N.Y. Its development was led by Dr. Jim Houck of Cornell.
The NASA Astrobiology Institute, founded in 1997, is a partnership between NASA,
16 major U.S. teams and six international consortia.
For artist concepts, graphics and more information about Spitzer, visit
http://www.spitzer.caltech.edu/spitzer/ . For more information about the NASA
Astrobiology Institute, visit http://nai.arc.nasa.gov/ . For more information about
NASA and agency programs on the Web, visit http://www.nasa.gov/home/ .
Whitney Clavin (818) 354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
2005-160
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