Young Stars Flicker Amidst Clouds of Gas and Dust

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

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@jpl.nasa.gov

Image advisory: 2012-052 Feb. 29, 2012

Young Stars Flicker Amidst Clouds of Gas and Dust

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2012-052&cid=release_2012-052

PASADENA, Calif. – Astronomers have spotted young stars in the Orion nebula changing
right before their eyes, thanks to the European Space Agency's Herschel Space Observatory
and NASA's Spitzer Space Telescope. The colorful specks -- developing stars strung across
the image -- are rapidly heating up and cooling down, speaking to the turbulent, rough-and-
tumble process of reaching full stellar adulthood.

The image can be viewed at:
http://www.nasa.gov/mission_pages/herschel/multimedia/pia13959.html

The rainbow of colors represents different wavelengths of infrared light captured by both
Spitzer and Herschel. Spitzer is designed to see shorter infrared wavelengths than Herschel.
By combining their observations, astronomers get a more complete picture of star formation.
NASA's Jet Propulsion Laboratory in Pasadena, Calif., manages the Spitzer mission for
NASA, and also plays an important role in the European Space Agency-led Herschel mission.

In the portion of the Orion nebula pictured, the telescopes' infrared vision reveals a host of
embryonic stars hidden in gas and dust clouds. These stars are at the very earliest stages of
evolution.

A star forms as a clump of this gas and dust collapses, creating a warm glob of material fed by
an encircling disk. In several hundred thousand years, some of the forming stars will accrete
enough material to trigger nuclear fusion at their cores, and then blaze into stardom.

Herschel mapped this region of the sky once a week for six weeks in the late winter and
spring of 2011. To monitor for activity in protostars, Herschel's Photodetector Array Camera
and Spectrometer probed long infrared wavelengths of light that trace cold dust particles,
while Spitzer gauged the warmer dust emitting shorter infrared wavelengths. In this data,
astronomers noticed that several of the young stars varied in their brightness by more than 20
percent over just a few weeks. As this twinkling comes from cool material emitting infrared
light, the material must be far from the hot center of the young star, likely in the outer disk or
surrounding gas envelope. At that distance, it should take years or centuries for material to
spiral closer in to the growing starlet, rather than mere weeks.

A couple of scenarios under investigation could account for this short span. One possibility is
that lumpy filaments of gas funnel from the outer to the central regions of the star,
temporarily warming the object as the clumps hit its inner disk. Or, it could be that material
occasionally piles up at the inner edge of the disk and casts a shadow on the outer disk.

"Herschel's exquisite sensitivity opens up new possibilities for astronomers to study star
formation, and we are very excited to have witnessed short-term variability in Orion
protostars," said Nicolas Billot, an astronomer at the Institut de Radioastronomie
Millimétrique (IRAM) in Grenada, Spain who is preparing a paper on the findings along with
his colleagues. "Follow-up observations with Herschel will help us identify the physical
processes responsible for the variability."

Herschel is a European Space Agency cornerstone mission, with science instruments provided
by consortia of European institutes and with important participation by NASA. NASA's
Herschel Project Office is based at JPL. JPL contributed mission-enabling technology for two
of Herschel's three science instruments. The NASA Herschel Science Center, part of the
Infrared Processing and Analysis Center at the California Institute of Technology in
Pasadena, supports the United States astronomical community. Caltech manages JPL for
NASA.

More information is online at http://www.herschel.caltech.edu, http://www.nasa.gov/herschel
and http://www.esa.int/SPECIALS/Herschel/index.html .

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