NASA'S Spitzer Sees Light of Lonesome Stars

Oct. 24, 2012

J.D. Harrington
Headquarters, Washington
202-358-5241
j.d.harrington@nasa.gov

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


RELEASE: 12-374

NASA'S SPITZER SEES LIGHT OF LONESOME STARS

WASHINGTON -- A new study using data from NASA's Spitzer Space
Telescope suggests a cause for the mysterious glow of infrared light
seen across the entire sky. It comes from isolated stars beyond the
edges of galaxies. These stars are thought to have once belonged to
the galaxies before violent galaxy mergers stripped them away into
the relatively empty space outside of their former homes.

"The infrared background glow in our sky has been a huge mystery,"
said Asantha Cooray of the University of California at Irvine (UC
Irvine), lead author of the new research published in the journal
Nature. "We have new evidence this light is from the stars that
linger between galaxies. Individually, the stars are too faint to be
seen, but we think we are seeing their collective glow."

The findings disagree with another theory explaining the same
background infrared light observed by Spitzer. A group led by
Alexander "Sasha" Kashlinsky of NASA's Goddard Space Flight Center in
Greenbelt, Md., proposed in June this light, which appears in Spitzer
images as a blotchy pattern, is coming from the very first stars and
galaxies.

In the new study, Cooray and colleagues looked at data from a larger
portion of the sky, called the Bootes field, covering an arc
equivalent to 50 full Earth moons. These observations were not as
sensitive as those from the Kashlinsky group's studies, but the
larger scale allowed researchers to better analyze the pattern of the
background infrared light.

"We looked at the Bootes field with Spitzer for 250 hours," said
co-author Daniel Stern of NASA's Jet Propulsion Laboratory (JPL) in
Pasadena, Calif. "Studying the faint infrared background was one of
the core goals of our survey, and we carefully designed the
observations in order to directly address the important, challenging
question of what causes the background glow."

The team concluded the light pattern of the infrared glow is not
consistent with theories and computer simulations of the first stars
and galaxies. Researchers say the glow is too bright to be from the
first galaxies, which are thought not to have been as large or as
numerous as the galaxies we see around us today. Instead, the
scientists propose a new theory to explain the blotchy light, based
on theories of "intracluster" or "intrahalo" starlight.

Theories predict a diffuse smattering of stars beyond the halos, or
outer reaches, of galaxies, and in the spaces between clusters of
galaxies. The presence of these stars can be attributed to two
phenomena. Early in the history of our universe as galaxies grew in
size, they collided with other galaxies and gained mass. As the
colliding galaxies became tangled gravitationally, strips of stars
were shredded and tossed into space. Galaxies also grow by swallowing
smaller dwarf galaxies, a messy process that also results in stray
stars.

"A light bulb went off when reading some research papers predicting
the existence of diffuse stars," Cooray said. "They could explain
what we are seeing with Spitzer."

More research is needed to confirm this sprinkling of stars makes up a
significant fraction of the background infrared light. For instance,
it would be necessary to find a similar pattern in follow-up
observations in visible light. NASA's upcoming James Webb Space
Telescope (JWST) might finally settle the matter for good.

"The keen infrared vision of the James Webb Telescope will be able to
see some of the earliest stars and galaxies directly, as well as the
stray stars lurking between the outskirts of nearby galaxies," said
Eric Smith, JWST's deputy program manager at NASA Headquarters in
Washington. "The mystery objects making up the background infrared
light may finally be exposed."

Other authors include Joseph Smidt, Francesco De Bernardis, Yan Gong
and Christopher C. Frazer of UC Irvine; Matthew L. N. Ashby of the
Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass; Peter
R. Eisenhardt of JPL; Anthony H. Gonzalez of the University of
Florida in Gainesville; Christopher S. Kochanek of Ohio State
University in Columbus; Szymon Koz��owski of Ohio State and the Warsaw
University Observatory in Poland; and Edward L. Wright of the
University of California, Los Angeles.

JPL manages the Spitzer Space Telescope mission for NASA's Science
Mission Directorate in Washington. Science operations are conducted
at the Spitzer Science Center at the California Institute of
Technology (Caltech) in Pasadena. Data are archived at the Infrared
Science Archive housed at the Infrared Processing and Analysis Center
at Caltech. Caltech manages JPL for NASA.

For more information about Spitzer, visit:

http://www.nasa.gov/spitzer


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