Gas explosion observed preceding supernova

Nature : A massive star, about 500 million light-years from Earth, blew off a parcel of gas just 40 days before the star went supernova. The discovery was made by astronomers studying images captured by the Palomar Transient Factory (PTF), an astronomical wide-field survey based at the Palomar Observatory in California. The fully automated PTF constantly sweeps the sky, looking for supernovae, transiting planets, and other transient events. After discovering supernova SN 2010mc, Eran Ofek of the Weizmann Institute of Science in Rehovot, Israel, and his colleagues searched earlier images to see whether they could detect the ejection of material that many believe occurs years or decades before such type II supernovae explode. It is thought that in the late stages of a massive star’s evolution, energy generated by the core burning is carried by oscillations from the interior to the exterior and expelled. Whether such a blast triggers a star to go supernova, however, needs to be investigated further.