By Nadia Drake
Light from the universe’s very first stars still lingers in space. Now, astronomers have a new way to catch it: Distant, ultra-bright galaxies that act as cosmic beacons, capturing relict photons in a blaze of gamma rays.
But it’s not just these earliest photons that are snared; photons from every star that ever shone can be captured. “We now have constraints on the total number of stars that ever formed,” Volker Bromm, an astronomer at the University of Texas at Austin, says of the new way to see old light, described online November 1 in Science. “It provides us with a review of the entire history of cosmic star formation, including the very first epochs of star formation in the very early universe.”
Studying these stellar fingerprints will help astronomers learn more about the universe’s earliest years — and its first inhabitants, which are too far away to be seen directly. Now roughly 13.7 billion years old, the universe is thought to have switched on the first stars about 400 million years after the Big Bang.