Spitzer Finds Organics and Water Where New Planets May Grow

http://www.jpl.nasa.gov/news/news.cfm?release=2008-042

Spitzer Finds Organics and Water Where New Planets May Grow
Jet Propulsion Laboratory
March 13, 2008

Researchers using NASA's Spitzer Space Telescope have discovered large
amounts of simple organic gases and water vapor in a possible
planet-forming region around an infant star, along with evidence that
these molecules were created there. They've also found water in the
same
zone around two other young stars.

By pushing the telescope's capabilities to a new level, astronomers
now
have a better view of the earliest stages of planetary formation,
which
may help shed light on the origins of our own solar system and the
potential for life to develop in others. John Carr of the Naval
Research
Laboratory, Washington, and Joan Najita of the National Optical
Astronomy Observatory, Tucson, Ariz., developed a new technique using
Spitzer's infrared spectrograph to measure and analyze the chemical
composition of the gases within protoplanetary disks. These are
flattened disks of gas and dust that encircle young stars. Scientists
believe they provide the building materials for planets and moons and
eventually, over millions of years, evolve into orbiting planetary
systems like our own.

"Most of the material within the disks is gas," said Carr, "but until
now it has been difficult to study the gas composition in the regions
where planets should form. Much more attention has been given to the
solid dust particles, which are easier to observe." In their project,
Carr and Najita took an in-depth look at the gases in the planet-
forming
region in the disk around the star AA Tauri. Less than a million years
old, AA Tauri is a typical example of a young star with a
protoplanetary
disk.

With their new procedures, they were able to detect the minute
spectral
signatures for three simple organic molecules--hydrogen cyanide,
acetylene and carbon dioxide--plus water vapor. In addition, they
found
more of these substances in the disk than are found in the dense
interstellar gas called molecular clouds from which the disk
originated.
"Molecular clouds provide the raw material from which the
protoplanetary
disks are created," said Carr. "So this is evidence for an active
organic chemistry going on within the disk, forming and enhancing
these
molecules."

Spitzer's infrared spectrograph detected these same organic gases in a
protoplanetary disk once before. But the observation was dependent on
the star's disk being oriented in just the right way. Now researchers
have a new method for studying the primordial mix of gases in the
disks
of hundreds of young star systems.

Astronomers will be able to fill an important gap--they know that
water
and organics are abundant in the interstellar medium but not what
happens to them after they are incorporated into a disk. "Are these
molecules destroyed, preserved or enhanced in the disk?" said Carr.
"Now
that we can identify these molecules and inventory them, we will have
a
better understanding of the origins and evolution of the basic
building
blocks of life--where they come from and how they evolve." Carr and
Najita's research results appear in the March 14 issue of Science.

Taking advantage of Spitzer's spectroscopic capabilities, another
group
of scientists looked for water molecules in the disks around young
stars
and found them--twice. "This is one of the very few times that water
vapor has been directly shown to exist in the inner part of a
protoplanetary disk--the most likely place for terrestrial planets to
form," said Colette Salyk, a graduate student in geological and
planetary sciences at the California Institute of Technology in
Pasadena. She is the lead author on a paper about the results in the
March 20 issue of Astrophysical Journal Letters.

Salyk and her colleagues used Spitzer to look at dozens of young stars
with protoplanetary disks and found water in many. They honed in on
two
stars and followed up the initial detection of water with
complementary
high-resolution measurements from the Keck II Telescope in Hawaii.
"While we don't detect nearly as much water as exists in the oceans on
Earth, we see essentially only the disk's surface, so the implication
is
that the water is quite abundant," said Geoffrey Blake, professor of
cosmochemistry and planetary sciences at Caltech and one of the
paper's
co-authors.

"This is a much larger story than just one or two disks," said Blake.
"Spitzer can efficiently measure these water signatures in many
objects,
so this is just the beginning of what we will learn."

"With upcoming Spitzer observations and data in hand," Carr added, "we
will develop a good understanding of the distribution and abundance of
water and organics in planet-forming disks."

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the
Spitzer
Space Telescope mission for NASA's Science Mission Directorate,
Washington. Science operations are conducted at the Spitzer Science
Center at Caltech, also in Pasadena. Caltech manages JPL for NASA.

The National Optical Astronomy Observatory, Tucson, Ariz., is operated
by the Association of Universities for Research in Astronomy, under a
cooperative agreement with the National Science Foundation. The W.M.
Keck Observatory is funded by Caltech, the University of California
and
NASA, and is managed by the California Association for Research in
Astronomy, Kamuela, Hawaii.

For more information about Spitzer, visit
http://www.spitzer.caltech.edu/spitzer and http://www.nasa.gov/spitzer
..

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Media Contact: Rosemary Sullivant 818-354-2274
Jet Propulsion Laboratory, Pasadena, Calif.
Rosemary.Sullivant@xxxxxxxxxxxx
.

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