At least once a day, a brilliant flash of gamma rays appears from a random direction. After a three-decade hunt, astronomers may have tracked down the sources of these blasts of energetic, invisible radiation. A pair of gas clouds in a nearby galaxy appears to be the tortured remains of two ancient gamma-ray bursts.
Daniel Wang, an astrophysicist at Northwestern University, was studying images of the Pinwheel galaxy, or M101, when he noticed the two unusual objects. They looked like the remains of supernovas, rare and powerful stellar explosions, but were far too bright. Wang believes he has spotted the aftermath of hypernovas, theoretical events in which dying stars blow off their outer layers and collapse into black holes. They may be the fiercest blasts since the beginning of the universe.
When gamma-ray bursts were first detected by military satellites in the 1960s, nobody knew where they came from. Scientists have since deduced that they occur in the most distant corners of the cosmos and have wondered what could possibly power them. Hypernovas could do the trick. These explosions probably occur among young, massive stars, so gamma-ray bursts may contain a hidden message about how galaxies evolve. "From the distribution of gamma-ray bursts, we may be able to infer the history of star formation in the universe," Wang says.
