An ultrapowerful supernova discovered in 2006 may blow its top again. Burning 100 times brighter than a typical supernova, SN 2006gy maintained full strength for an amazing three months. To explain the massive outburst, researchers invoked a mechanism called pair instability, in which high-energy gamma rays inside the star convert into pairs of electrons and positrons, draining stellar energy that would normally help maintain its internal pressure. That sapping leads to a premature collapse, liberating vast amounts of energy and light. Astrophysicists now report that SN 2006gy's brightness changes fit a model of pulsating pair instability. In this scenario, the initial implosion of a 110-solar-mass star would shed several suns' worth of mass before igniting the star's carbon and oxygen fuel, temporarily halting the collapse. Roughly seven years later pair instability would cause a second breakdown that would emit a smaller but faster pulse of material. The study appears in the November 15, 2007, Nature.
This article was originally published with the title "Brightest Supernova May Reignite" in Scientific American 298, 2, 30 (February 2008)