Written by Alan Buis
NASA’s Jet Propulsion Laboratory
Pasadena, CA – 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, 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 analyze better 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 in Pasadena, CA. “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.”
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.
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 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 .