Tiny flicker spotted in night sky revealed to be largest cosmic explosion ever seen

It started as an unremarkable flicker in the night sky. But closer observations revealed that astronomers had captured the largest cosmic explosion ever witnessed, an event thought to have been triggered by a giant cloud of gas being gobbled by a supermassive black hole.

- Hannah Devlin

The flare-up, traced to 8bn light years away, is more than 10 times brighter than any known supernova and has currently lasted more than three years, making it the most energetic explosion on record.

"It went unnoticed for a year as it gradually got brighter," said Dr Philip Wiseman, an astronomer at Southampton University who led the observations.

It was only when follow-up observations revealed how distant it was that astronomers appreciated the event's almost unimaginable scale.

"We've estimated it's a fireball 100 times the size of the solar system explosion, known as AT2021lwx, is the result of a vast cloud of gas, possibly thousands of times larger than our sun, plunging into the inescapable mouth of a supermassive black hole.

The cloud of gas may have originated from the large dusty "doughnut" that typically surrounds black holes - although it is not clear what may have knocked it off course from its orbit and down the cosmic sinkhole.