ANU scientists help solve mystery of exploding white dwarf star system
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ANU scientists help solve mystery of exploding white dwarf star system

Scientists believe they have finally found the trigger behind an explosive galactic phenomenon.

Researchers from the Australian National University, in conjunction with international experts, have been studying the causes of massive explosions involving binary white dwarf star systems.

An artist's impression of a white dwarf supernova explosion.

An artist's impression of a white dwarf supernova explosion.Credit:Russell Kightley/ANU

"What triggers these supernovae explosions is uncertain," said Professor Lilia Ferrario from the ANU Mathematical Sciences Institute.

The team believed some explosions were caused when a super dense white dwarf – essentially a small dead star – sucked fuel away from a giant star with which it shares an orbit.

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"This discovery gives weight to a theory that a white dwarf star devours material from its giant star companion until the white dwarf explodes as a supernova," Professor Ferrario said.

Professor Ferrario said the team of researchers had made the find while examining a piece of "shrapnel" from a supernova explosion millions of years ago.

"The mass that accumulated on the white dwarf caused a thermonuclear runaway and a violent explosion that destroyed the binary system," she said.

"A piece of shrapnel, which is the size of a small star, was flung into space and travelled for millions of years through the Milky Way."

The notable thing about white dwarf stars, Professor Ferrario said, is that they would never explode if left to their own devices.

Two theories had therefore been put forward to explain the unusual circumstances in which they did blow up.

"One suggests that two white dwarfs merge to form a single ultra-massive white dwarf," she said.

"While the other theory envisages a white dwarf devouring material from its companion star.

"In both cases, when the white dwarf becomes 1.4 times as massive as the Sun, a thermonuclear explosion is ignited leading to a partial or total disruption of the white dwarf."

The study was published in the prestigious academic journal Science, and involved a consortium of researchers from the Czech Republic, Germany, Hungary, the United States and Canada.