Super-rare supernova outshines the rest

U. TEXAS-AUSTIN (US) — At its peak, a newly found supernova emitted enough energy in one second to satisfy the power needs of the U.S. for one million times longer than the universe has existed.

Supernova 2008am, the most luminous exploding star ever observed, is 3.7 billion light years away and owes its extreme brightness to the interaction between the explosion shockwave and a shell of material previously expelled from the star.

At its most bright, it was 100 billion times brighter than the Sun.

Details of the research are reported in The Astrophysical Journal.

SN 2008am’s extraordinary luminosity most likely comes from interaction between the debris from the star’s explosion running into an envelope of gas around the star that it had previously ejected, says Emmanouil (Manos) Chatzopoulos, graduate student at the University of Texas-Austin.

The model is called circumstellar interaction.

The progenitor star for this supernova might have been of the type known as a “luminous blue variable” that puff off layers of material in episodes. The most famous example is Eta Carinae.

Prior to this discovery, the Texas Supernova Search’s found the first two brightest supernovae ever in SN 2005ap and 2006gy and found five of the dozen published examples of this new class of stars, which it has dubbed “super-luminous supernovae,” or SLSNe.

SLSNe are about 100 times brighter than standard core-collapse supernovae, but extremely rare. Normal supernovae go off at a rate of about one per century in a galaxy; SLSNe may be more than a thousand times more rare.

“We’re now in the process of converting our discoveries into real science rather than just a new thing,” says astronomer J. Craig Wheeler. “That makes it a little bit less flashy, but of course that’s where the science really is, digging deeply into the nature of these very bright events. This new supernova has given us important new clues to their behavior.”

“For the first time, we’re probing high-mass stellar death,” says Chatzopoulos. “The traditional ideas we have about how supernovae are powered, why they are so bright, do not seem to apply for the case of these super-luminous supernovae. There are other mechanisms involved.”

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