Astronomers capture the largest cosmic explosion ever witnessed

Astronomers have captured the largest cosmic explosion ever witnessed, an event thought to have been triggered by a giant cloud of gas being consumed by a supermassive black hole, experts at Southampton University have revealed.

The flare-up, traced to 8bn light years away, is reportedly said to have been more than ten times brighter than any known supernova (an exploding star) and has so far lasted more than three years, making it the most energetic explosion on record.

Scientists believe that the explosion, known as AT2021lwx, is the result of a vast cloud of gas, possibly thousands of times larger than our sun, plunging into a supermassive black hole.

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

It was only when follow-up analysis revealed how distant it was that astronomers appreciated the event’s awesomely gargantuan scale.

“We’ve estimated it’s a fireball 100 times the size of the solar system with a brightness about 2tn times the sun’s,” Wiseman said.

“In three years, this event has released about 100 times as much energy as the sun will in its 10bn-year lifetime.”

The magnitude of the cosmic explosion was outside the plausible range for it to be defined as a supernova.

As a result, astronomers began to assess the explosion as a tidal disruption event, which is another common situation that instigates bright flashes in the night sky.

These events typically involve a star straying too close to a black hole and being part swallowed, with the remainder being stretched into what you might compare to a swirling disc.

However simulations suggested a star up to 15 times the mass of the sun would have been required to account for AT2021lwx.

“Encountering such a huge star is very rare, so we think a much larger cloud of gas is more likely,” Wiseman said.

AT2021lwx is not the brightest phenomenon ever witnessed, however.

A brighter gamma-ray burst, known as GRB 221009A, was spotted last year (2022), but this event lasted only minutes.

The explosion was first detected in 2020 by the Zwicky Transient Facility in California, which surveys the night sky for sudden increases in brightness that could signal cosmic events such as passing asteroids, supernovae and comets.

The event initially did not stand out, but when follow-up observations allowed its distance to be calculated, astronomers realised they had captured an incredibly rare event.