Stars give warnings when they are about to explode in a supernova

Astronomers from the Liverpool John Moores University (LJMU) and the University of Montpellier have created an “early warning” system that can alert astronomers when a massive star is about to end its life in supernova explosion. In the last phase of their lives, these massive “red supergiant” stars will become around a hundred times fainter. This happens because material suddenly accumulates around the star, obscuring our view of it.
For the first time, researchers have simulated how such massive stars seemingly fade away and disappear as they enter a pre-explosion phase. This research has been published in the journal Monthly Notices of the Royal Astronomical Society.

“The dense material almost completely obscures the star, making it 100 times fainter in the visible part of the spectrum. This means that the day before the star explodes, you likely wouldn’t be able to see it was there,” said Ben Davies, corresponding author of the research article. Davies is part of LJMU’s Astrophysics Research Institute.
Till now, astronomers did not know hold long it takes for these massive stars to start developing this pre-explosion “cocoon” of material. In the new study, researchers looked at how red supergiants look when they are embedded within these envelopes of material. The astronomers searched through old telescope archives and looked at images of these red supergiant stars taken around a year before their explosion. They found that the stars appear normal. This means that this cocoon is formed in less than a year, which is akin to the blink of an eye in the cosmic context.
“Until now, we’ve only been able to get detailed observations of supernovae hours after they’ve already happened. With this early-warning system we can get ready to observe it in real-time, to point the world’s best telescopes at it, and watch the surface of the star getting literally ripped apart in front of our eyes,” added Davies.