Supernova shows secrets of its brightness

A NASA orbiting telescope has observed the first evidence of a supernova shock wave breaking through a cocoon of gas around the star, astronomers say. The findings by the Chandra X-ray Observatory may help explain why some supernova explosions are more powerful than others, a release by the Chandra group at Harvard University reported Tuesday. The supernova in a galaxy about 160 million light years from Earth was first spotted by astronomers on Nov. 3, 2010, and was one of the most luminous that has ever been detected in X-rays, the researchers said. In the first Chandra observation of the supernova, the X-rays from the explosion's blast wave were strongly absorbed by a cocoon of dense gas around the supernova formed by gas blown away from the massive star before it exploded. In a second observation almost a year later, there was much less absorption of X-ray emission, indicating that the blast wave from the explosion had broken out of the surrounding cocoon. This findings suggest some unusually luminous supernovas are caused by the blast wave from their explosion ramming into the material around it, astronomers said.