Astronomers find ‘largest ever’ cosmic explosion by chance

12 May 2023

An artist’s impression of a black hole accretion. Image: John A Paice

Data suggests that the explosion is roughly 8bn light years away and nearly 100 times brighter than all the stars in our galaxy combined.

A new investigation has revealed a cosmic explosion that is 10 times brighter than any known supernova (exploding star).

The cosmic explosion – called AT2021lwx – has lasted for more than three years. Most supernovae are only visible for a few months.

The explosion is believed to have taken place nearly 8bn light years away, when the universe was around 6bn years old. Despite the immense distance, it is large enough to still be detectable by a network of telescopes.

The investigation was led by the University of Southampton, in collaboration with Queen’s University Belfast (QUB).

QUB researchers led the search for cosmic explosions using the Asteroid Terrestrial-impact Last Alert System, which is a network of robotic telescopes that monitor the night sky.

From analysing the data, the researchers believe the massive explosion is a result of vast cloud of gas being violently disrupted by a supermassive black hole. Astronomers believe these types of black holes lie in the centre of virtually all large galaxies.

The researchers said these types of events are very rare and nothing on this scale has been witnessed before. The data suggests that the explosion is nearly 100 times brighter than all the stars in our galaxy combined.

The research was led by Dr Philip Wiseman, a research fellow at the University of Southampton. He said it was “immediately very unusual” to spot a cosmic event like this being bright for so long.

“We came upon this by chance, as it was flagged by our search algorithm when we were searching for a type of supernova,” Wiseman said.

QUB’s Dr Matt Nicholl helped to analyse the brightness of the explosion and said the team originally thought the explosion came from a black hole consuming a passing star.

“But our models showed that the black hole would have to have swallowed up 15 times the mass of our Sun to stay this bright for this long,” Nicholl said.

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

The researchers said the only things in the universe that are as bright as AT2021lwx are quasars, which are supermassive black holes that have a constant flow of gas falling into them. In 2019, an ancient quasar was discovered that had the brightness equivalent to 600trn suns.

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Leigh Mc Gowran is a journalist with Silicon Republic