Astronomers Find Stellar Cradle Where Planets Form

ASTRONOMERS FIND STELLAR CRADLE WHERE PLANETS FORM

http://www.news.uiuc.edu/news/07/1129cradle.html
Nov. 29, 2007

CONTACT:
James E. Kloeppel, Physical Sciences Editor
1-217-244-1073 kloeppel@xxxxxxxx

CHAMPAIGN, Ill. - Astronomers at the University of Illinois have found
the
first clear evidence for a cradle in space where planets and moons
form. The
cradle, revealed in photographs taken with NASA's Spitzer Space
Telescope,
consists of a flattened envelope of gas and dust surrounding a young
protostar.

"We are seeing this object in the early stages of stellar birth,"
said
U. of I. astronomy professor Leslie Looney, the lead author of a
paper
accepted for publication in Astrophysical Journal Letters.
"Eventually,
the protostar will form into a star much like our sun, and the disk
will
form into planets and moons."

Located about 800 light-years away in the constellation Cepheus, the
object
is obscured by dust and therefore invisible to the eye. However, the
Spitzer
Space Telescope's sensitive infrared camera can penetrate the dust,
and
reveal the structures within. The brightest structure consists of an
enormous, almost linear flow of shocked molecular hydrogen gas
erupting from
the protostar's two magnetic poles. These bipolar jets are so long,
light
would take about 1 1/2 years to travel from one end to the other.

In star-formation theory, a cloud of gas and dust collapses to form a
star
and its planets. As the cloud collapses, it begins to rotate faster
and
faster, like a pirouetting ice skater pulling in her arms. The force
of the
growing magnetic field ejects some of the gas and dust along the
magnetic
axis, forming the bipolar jets seen in the photograph. "If material
was
not shed in this fashion, the protostar's spin would speed up so fast
it
would break apart," Looney said.

The planet-forming region is perpendicular to, and roughly centered on
the
polar jets. There, seen in silhouette against a bright background of
galactic infrared emission, is the flattened disk of a circumstellar
envelope. Theorized, but never before seen, the flattened disk is an
expected outcome for cloud-collapse theories that include magnetic
fields or
rotation. "Some theories had predicted that envelopes flatten as
they
collapse onto their stars and surrounding planet-forming disks,"
Looney
said, "but we hadn't seen any strong evidence of this until now."

With Looney, co-authors of the paper are former undergraduate student
John
Tobin (now at the University of Michigan) and graduate student Woojin
Kwon.

The Spitzer Space Telescope is operated by the Jet Propulsion
Laboratory at
the California Institute of Technology. Funding was provided by NASA.
To reach Leslie Looney, call 1-217-244-3615; e-mail: lwl@xxxxxxxx

.

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