A giant gamma-ray burst (GRB) has been detected that has astronomers scratching their heads.
Gamma ray bursts are some of the most powerful explosions in the Universe and are thought to be produced by the catastrophic destruction of stars.
But this new explosion, spotted a few billion lightyears outside our Galaxy and named GRB 250702B, was unlike any seen before, bringing this theory into question.
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"This event is unlike any other seen in 50 years of GRB observations," says Antonio Martin-Carrillo of University College Dublin and co-lead author of the study.
"Gamma-ray bursts are catastrophic events; they’re expected to go off just once because the source that produced them does not survive the dramatic explosion.
"This event baffled us, not only because it showed repeated powerful activity, but also because it seemed to be periodic, which has never been seen before."
To add to the mystery, while most gamma-ray bursts last just a few milliseconds or minutes, this one lasted a day.
"This is 100 to 1,000 times longer than most gamma-ray bursts," explains the study’s co-author Andrew Levan.
Various telescopes were trained on where the gamma-ray burst was thought to originate, with ESO’s Very Large Telescope placing it outside our Galaxy.
The fact that it’s so far away means that the explosion must have been incredibly powerful.
"We’re still not sure what produced this or if we can ever really find out," says Martin-Carrillo, "but with this research, we’ve made a huge step towards understanding this extremely unusual object."
One possible cause for the gamma-ray burst could be a massive star collapsing into itself, releasing enormous amounts of energy in the process.
"If this is a massive star, it is a collapse unlike anything we have ever witnessed before," says Levan, referring to the fact that, if it was a massive star, the gamma-ray burst would likely have lasted just a few seconds.
The other cause could be a star being ripped apart by a black hole.
That, the team say, could produce a day-long GRB, but to explain other aspects of the explosion would mean an unusual star being destroyed by an even more unusual black hole.
