Shining Starlight on the Dark Cocoons of Star Birth

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE 818-354-5011
http://www.jpl.nasa.gov

Whitney Clavin/Guy Webster 818-354-4673/6278
Jet Propulsion Laboratory, Pasadena, Calif.
whitney.b.clavin@jpl.nasa.gov/guy.webster@jpl.nasa.gov

Feature September 23, 2010

Shining Starlight on the Dark Cocoons of Star Birth

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2010-311&cid=release_2010-311

Astronomers have discovered a new, cosmic phenomenon, termed "coreshine,"
which is revealing new information about how stars and planets come to be.

The scientists used data from NASA's Spitzer Space Telescope to measure
infrared light deflecting off cores -- cold, dark cocoons where young stars and
planetary systems are blossoming. This coreshine effect, which occurs when
starlight from nearby stars bounces off the cores, reveals information about their
age and consistency. In a new paper, to be published Friday, Sept. 24, in the
journal Science, the team reports finding coreshine across dozens of dark
cores.

"Dark clouds in our Milky Way galaxy, far from Earth, are huge places where
new stars are born. But they are shy and hide themselves in a shroud of dust so
that we cannot see what happens inside," said Laurent Pagani of the
Observatoire de Paris and the Centre National de la Recherche Scientifique,
both in France. "We have found a new way to peer into them. They are like
ghosts because we see them but we also see through them."

Pagani and his team first observed one case of the coreshine phenomenon in
2009. They were surprised to see that starlight was scattering off a dark core in
the form of infrared light that Spitzer could see. They had thought the grains of
dust making up the core were too small to deflect the starlight; instead, they
expected the sunlight would travel straight through. Their finding told them that
the dust grains were bigger than previously thought -- about 1 micron instead of
0.1 micron (a typical human hair is about 100 microns).

That might not sound like a big difference, but it can significantly change
astronomers' models of star and planet formation. For one thing, the larger grain
size means that planets -- which form as dust circling young stars sticks
together -- might take shape more quickly. In other words, the tiny seeds for
planet formation may be forming very early on, when a star is still in its pre-
embryonic phase.

But this particular object observed in 2009 could have been a fluke. The
researchers did not know if what they found was true of other dark clouds -- until
now. In the new study, they examine 110 dark cores, and find that about half of
them exhibit coreshine.

The finding amounts to a new tool for not only studying the dust making up the
dark cores, but also for assessing their age. The more developed star-forming
cores will have larger dust grains, so, using this tool, astronomers can better
map their ages across our Milky Way galaxy. Coreshine can also help in
constructing three-dimensional models of the cores -- the deflected starlight is
scattered in a way that is dependent on the cloud structures.

Said Pagani, "We're opening a new window on the realm of dark, star-forming
cores."

Other authors are Aurore Bacmann of the Astrophysics Laboratory of Grenoble,
France, and Jürgen Steinacker, Amelia Stutz and Thomas Henning of the Max-
Planck Institute for Astronomy, Germany. Steinacker is also with the
Observatoire de Paris, and Stutz is also with the University of Arizona, Tucson.

The Spitzer measurements are based on data from the mission's public archive,
taken before the telescope ran out of its liquid coolant in May 2009 and began
its current warm mission.

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 the
California Institute of Technology, also in Pasadena. Caltech manages JPL for
NASA. For more information about Spitzer, visit http://spitzer.caltech.edu/ and
http://www.nasa.gov/spitzer .

-end-

To remove yourself from this mailing, please go to http://www.kintera.org/TR.asp?a=erJLL2OEJaKKL8I&s=hhLWJYMBLdIIKXMHIrH&m=ctKPL0OGKkIXJfL

To remove yourself from all mailings from NASA Jet Propulsion Laboratory, please go to http://www.kintera.org/TR.asp?a=huLRIbPQIdJRJiL&s=hhLWJYMBLdIIKXMHIrH&m=ctKPL0OGKkIXJfL