Massive stars send out ‘warning’ before they are about to explode and die

An artist's impression of Betelgeuse's supernova (European Southern Observatory/L. Calçada)

Massive stars send out something of an ‘early warning signal’ when they are about to explode into a supernova and die, scientists have found.

When a star is reaching the last stage of its life, it will suddenly go about a hundred times more faint than usual, they say. That will last for a few months and then the star will die out, they say.

The dimming effect happens when material suddenly accumulates around the dying star, blocking out the light, they say.

The finding could help astronomers watch such stars as they explode – rather than noticing them afterwards, they say.

Scientists were previously unsure how long this process takes. Researchers are now able to say that it will last a few months, and have been able to better understand what stars might look like as they are getting wrapped up in those “cocoons” before they explode.

“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.

“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 them real-time, to point the world’s best telescopes at the precursor stars, and watch them getting literally ripped apart in front of our eyes.”

The new findings are reported in a paper, ‘Explosion Imminent: the appearance of Red Supergiants at the point of core-collapse’, published in the Monthly Notices of the Royal Astronomical Society.