First Stars or Stray Stars? A Cosmic Infrared Mystery

Our sky is filled with a diffuse background glow, known as the cosmic infrared background. Much of the light is from galaxies we know about, but previous Spitzer measurements have shown an extra component of unknown origin. Researchers have proposed two competing theories for the source of this light, including the very first galaxies and black holes (left, artist's concept), or collections of stars tossed out from galaxy collisions (right, Hubble image).

The flung-out stars are produced later in the history of the universe than the first galaxies. An example of such a tidal stripping process can be seen in the image from NASA's Hubble Space Telescope, where billions of stars, too faint to be seen individually, are torn from their parent galaxies in milky tidal streams.

New evidence from NASA's Cosmic Infrared Background Experiment, or CIBER, strongly suggests that the glow is not from the first galaxies, but is better explained by stars tossed out during the assembly of galaxies.

Caltech manages JPL for NASA. The work was supported by NASA, with initial support provided by JPL's Director's Research and Development Fund. Japanese participation in CIBER was supported by the Japan Society for the Promotion of Science and the Ministry of Education, Culture, Sports, Science and Technology.Korean participation in CIBER was supported by the Korean Astronomy and Space Science Institute.

For more information about CIBER, visit http://ciber.caltech.edu/rocket.html.