Astronomers led by graduate student Emmanouil "Manos" Chatzopoulos and Dr. J. Craig Wheeler of The University of Texas at Austin have found another extremely bright, rare supernova to add to the new class of exploding stars that University of Texas astronomers identified a few years ago. Supernova 2008am is one of the most intrinsically bright exploding stars ever observed.
The team's research reveals that this supernova is the brightest "self-interacting" supernova yet discovered. In this type of stellar explosion, the extreme brightness is caused by interaction between the explosion shockwave and a shell of material previously expelled from the star. This research is published in the current issue of The Astrophysical Journal.
Supernova 2008am is 3.7 billion light-years away. At its peak luminosity, it was over 100 billion times brighter than the Sun. It emitted enough energy in one second to satisfy the power needs of the United States for one million times longer than the universe has existed. In-depth studies of this supernova are helping the team to understand the science behind this new class of exploding stars.
The supernova was discovered by the ROTSE Supernova Verification Project (RSVP, formerly called the Texas Supernova Search), which uses the 18-inch robotic ROTSE IIIb Telescope at The University of Texas at Austin's McDonald Observatory.
It was followed up by astronomers using some of the world's largest ground-based telescopes, as well as telescopes in space, in a variety of wavelengths. These include the Hobby-Eberly Telescope, the Keck Telescope, PAIRITEL, the Very Large Array, and the Swift satellite.
Chatzopoulos' detailed analysis of the light from SN 2008am revealed that is not a pair-instability supernova, the explosion of a massive star the light from which is powered by radioactive decay. Rather, this supernova'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 the star had previously ejected. This model is called "circumstellar interaction."
The researchers suspect that the progenitor star for this supernova might have been of the type known as a "luminous blue variable." These massive stars 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. The group has 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.
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