‘Zombie star’ amazes scientists by surviving multiple supernovae

'Zombie star' amazes scientists by surviving multiple supernovae

It’s the star that won’t die, even though it has exploded and appeared to go down in a blaze of glory multiple times. This superlong supernova may be the first of its kind.

The star, which lies half a billion light years away in the constellation of the Great Bear, is believed to exploded five times since 1954.

The mysterious object, named iPTF14hls, was first picked up in September 2014 but was not identified as an exploding star until January 2015.

Iair Arcavi, an astronomer at Las Cumbres Observatory in California said: “This is the weirdest supernova we’ve ever seen.

“It’s the first time we’ve seen multiple explosions in the same place.”

Mr Arcavi and his team have been perplexed by the phenomenon as usually when stars go supernova, they die in a single blast.

The astronomer said: ”This supernova breaks everything we thought we knew about how they work. It’s the biggest puzzle I’ve encountered in almost a decade of studying stellar explosions.”

The zombie star also has a number of puzzling attributes including shining brightly for 600 days – nearly two years – without appearing to fade.

When its brightness did fade it varied by as much as 50 per cent on an irregular timescale as if it was exploding over and over again.

At first, Mr Arcavi and his team thought that a nearby star in the Milky Way had simply wandered into the same position and blocked out the supernova.

He added: “I probably would have bet my car on it, but I’m glad I didn’t.

“We were astonished to find that it was the supernova.”

After discovering the exploding star three years ago, the scientists found archive data showing an explosion that occurred in 1954 in exactly the same location, suggesting the star somehow survived that explosion, only to detonate again in 2014.

The object may be the first known example of a Pulsational Pair Instability Supernova.

Daniel Kasen, from the University of California, Berkeley who co-authored the study, said: ”According to this theory, it is possible that this was the result of a star so massive and hot that it generated antimatter in its core.

“That would cause the star to go violently unstable, and undergo repeated bright eruptions over periods of years.”

That process could even repeat itself over decades before the star’s final explosion and collapse to a black hole.

Professor Stan Woosley, from the University of California who did not participate in the study, said: ”As of now, no detailed model has been published that can explain the observed emission and constant temperature of iPTF14hls, let alone the possible eruption 60 years ago.

“For now, the supernova offers astronomers their greatest thrill: something they do not understand.”

The British Journal Editors and Wire Services




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