NASA'S Spitzer Sees Light of Lonesome Stars

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Oct. 24, 2012

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

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


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 KozÅ?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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