A study using data from NASA's Spitzer Space Telescope suggests these stars once belonged to the galaxies before violent galactic mergers stripped them away into the relatively empty space outside of their former homes, the Jet Propulsion Laboratory in Pasadena, Calif., reported Wednesday.
"The infrared background glow in our sky has been a huge mystery," said lead study author Asantha Cooray of the University of California, Irvine. "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."
Astronomers used the Spitzer telescope to study a large portion of the sky, covering an arc equivalent to the diameters of 50 full Earth moons.
"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," JPL scientist Daniel Stern said.
The findings have led the astronomers to suggest this sprinkling of stars in the spaces between galaxies makes up a significant fraction of the background infrared light.