Cosmic glow may come from extragalactic stars

Nature : From 2010 to 2012, sounding rockets carried the Cosmic Infrared Background Experiment (CIBER) into space multiple times to look at the IR background, which is made up, in part, of myriad distant and unresolved galaxies. After eliminating light from the Milky Way, Michael Zemcov of Caltech and his colleagues found that a significant portion of the light CIBER detected was not redshifted enough to have come from old galaxies. When they extrapolated the data to cover the entire universe, they realized that the light detected couldn’t have come from known galaxies. That finding suggested that the source of the light was stars scattered in the space between galaxies. Those stars could have escaped low-mass galaxies or been ejected by collisions of galaxies. However, the stars are too faint to be detected individually. By Zemcov and colleagues’ calculations, the number of extragalactic stars could equal the number of stars in all the known galaxies.