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Stellar Shell Explosion Triggers Star Death

International astronomers believe they may have observed a precursor explosion that warns observers that a supernova is taking place.

Within a day of witnessing this “red optical flash”, the researchers discovered a Type Ia supernova named MUSSES1604D. Type Ia supernovae arise from the thermonuclear explosion of white-dwarf stars that have cores of carbon and oxygen.

Follow-up observations carried out by eight telescopes around the world showed that this supernova phase is marked by a bright flash about half a day after the explosion of a type Ia supernova.

The astronomers found that the early-phase light, colour and spectrum of the supernova could be perfectly explained by a stellar shell explosion in which the accumulation of helium at the surface of the white dwarf first ignites. Shock waves generated by this precursor event then propagate inward to ignite carbon burning in the core of the white dwarf.

The observation is the first robust proof of a stellar shell explosion, which was first proposed in the early 1980s but had not been witnessed until now.

“Learning more about type Ia supernovae will help us chart the expansion of the Universe,” said Prof Jeremy Mould of Swinburne University, who was co-author of the report published in Nature.