Mystery behind brightest explosion ever seen is finally solved

Blast was pointed right at Earth, researchers believe

The mystery behind the brightest explosion ever seen has finally been solved.

In October last year, the Earth was hit by a blast that came to be known as the Brightest of All Time or BOAT. It was recorded by telescopes across the world, and scientists have been scrambling to explain it ever since.

The explosion was a gamma-ray burst, the most violent and energetic explosions anywhere in the universe. In just a few seconds, they can produce as much energy as the Sun will in its entire lifetime.

The gamma-ray burst officially known as GRB 221009A, but better known as the BOAT, is believed to have erupted when a massive star collapsed into a black hole. But scientists were unsure why exactly that example had shone so brightlythrough the cosmos.

Now researchers believe they may understand why that gamma-ray burst was quite so intense. It was pointed directly at Earth and pulled along a large amount of stellar material.

That’s according to a new paper published in the journal Science Advances. While scientists have suggested before that the brightness of the blast was the result of its angle, but some mystery remained: the edges of the jet could not be seen.

“The slow fade of the afterglow is not characteristic of a narrow jet of gas, and knowing this made us suspect there was an additional reason for the intensity of the explosion, and our mathematical models have borne this out,” said Hendrik Van Earthen from the University of Bath.

“Our work clearly shows that the GRB had a unique structure, with observations gradually revealing a narrow jet embedded within a wider gas outflow where an isolated jet would normally be expected.”

The discovery that the burst has different jets from those usually found in such powerful events helps explain the unusual behaviour, but also shows that GRBs do not always behave as expected.

“GRB 221009A represents a massive step forward in our understanding of gamma-ray bursts, and demonstrates that the most extreme explosions do not obey the standard physics assumed for garden variety gamma-ray bursts,” said Brendan O’Connor, GW graduate student and lead study author, said.

“GRB 221009A might be the equivalent Rosetta stone of long GRBs, forcing us to revise our standard theories of how relativistic outflows are formed in collapsing massive stars.”

The work is described in a new paper, ‘A structured jet explains the extreme GRB 221009’, published in the journal Science Advances.