SN 2006gy: brightest supernova ever seen

Stephen Withers
Tuesday, 08 May 2007 07:59

Science - Space

Supernova SN 2006gy, the brightest ever recorded, appears to be a previously undetected type, astronomers say.

Ground-based observations led to a pair of likely explanations: either a white dwarf exploded into a dense, hydrogen-rich environment, or it was the death of an extremely massive star.

But measurements made by NASA's Chandra orbiting X-ray observatory showed SN 2006gy was far too dim in the X-ray portion of the electromagnetic spectrum for the former explanation.

"This provides strong evidence that SN 2006gy was, in fact, the death of an extremely massive star," said Dave Pooley of the University of California at Berkeley, who led the Chandra observations.

How massive? "[A]s massive as a star can get, about 150 times that of our sun," said Nathan Smith from the University of California at Berkeley.

"Supernovas usually occur when massive stars exhaust their fuel and collapse under their own gravity," explained NASA officials, but what may have happened with SN 2006gy was that extremely high levels of gamma radiation from the star's core caused energy to transform to matter, and the drop in energy in turn caused the star to collapse.

The finding has led astronomers to pay extra attention to Eta Carinae, a massive star in the Milky Way. Like the star that formed SN 2006gy, Eta Carinae has ejected a large amount of matter, which could mean it will become a supernova. Since Eta Carinae is 32,000 times closer than SN2006gy, the result could be spectacular.

"We don't know for sure if Eta Carinae will explode soon, but we had better keep a close eye on it just in case," said Mario Livio of the Space Telescope Science Institute in Baltimore, who was not involved in the research. "Eta Carinae's explosion could be the best star-show in the history of modern civilization."