Water Hit With Young Star's Best Shot (Spitzer)
- From: baalke@xxxxxxxxxxxxx
- Date: Thu, 18 Sep 2008 12:48:53 -0700 (PDT)
http://www.jpl.nasa.gov/news/features.cfm?feature=1869
Water Hit With Young Star's Best Shot
Jet Propulsion Laboratory
September 18, 2008
Water is being blasted to pieces by a young star's laser-like jets,
according to new observations from NASA's Spitzer Space Telescope.
The discovery provides a better understanding of how water -- an
essential ingredient for life as we know it -- is processed in
emerging
solar systems.
"This is a truly unique observation that will provide important
information about the chemistry occurring in planet-forming regions,
and
may give us insights into the chemical reactions that made water and
even life possible in our own solar system," said Achim Tappe, of the
Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass.
A young star forms out of a thick, rotating cloud of gas and dust.
Like
the two ends of a spinning top, powerful jets of gas emerge from the
top
and bottom of the dusty cloud. As the cloud shrinks more and more
under
its own gravity, its star eventually ignites and the remaining dust
and
gas flatten into a pancake-like disk, from which planets will later
form. By the time the star ignites and stops accumulating material
from
its cloud, the jets will have died out.
Tappe and his colleagues used Spitzer's infrared eyes to cut through
the
dust surrounding a nascent star, called HH 211-mm, and get a better
look
at its jets. These particular jets are exceptionally young at 1,000
years old, and they are some of the most collimated, or focused,
known.
An instrument on Spitzer called a spectrometer analyzed light from one
of the jets, revealing information about its molecules.
To the astronomers' surprise, Spitzer picked up the signature of
rapidly
spinning fragments of water molecules, called hydroxyl, or OH. In
fact,
the hydroxyl molecules have absorbed so much energy (through a process
called excitation) that they are rotating around with energies
equivalent to 28,000 Kelvin (27,700 degrees Celsius). This far exceeds
normal expectations for gas streaming out of a stellar jet. Water,
which
is abbreviated H2O, is made up of two oxygen atoms and one hydrogen;
hydroxyl, or OH, contains one oxygen and one hydrogen atom.
The results reveal that the jet is ramming its head into a wall of
material, vaporizing ice right off the dust grains it normally coats.
The jet is hitting the material so fast and hard that a shock wave is
also being produced.
"The shock from colliding atoms and molecules generates ultraviolet
radiation, which will break up water molecules, leaving extremely hot
hydroxyl molecules," said Tappe.
Tappe said this same process of ice being vaporized off dust occurs in
our own solar system, when the sun vaporizes ice in approaching
comets.
In addition, the water that now coats our world is thought to have
come
from icy comets that vaporized as they rained down on a young Earth.
Tappe is the lead author of a paper on this topic, which was published
in a recent issue of the Astrophysical Journal. Co-authors on the
paper
include Charlie Lada, and August Muench, also of the Harvard-
Smithsonian
Center for Astrophysics; and J. H. Black, of the Chalmers University
of
Technology, in Onsala, Sweden.
------------------------------------------------------------------------
Media contact: Whitney Clavin/JPL
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0850
.
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