Astronomers find the largest explosion ever seen in the universe

An artist's impression of a huge cosmic explosion.

Astronomers have found the largest explosion ever witnessed in the universe - involving a huge blackhole and a gas cloud thousands of times the size of our sun.

The explosion is more than 10 times brighter than any known supernova and three times brighter than the brightest tidal disruption event, where a star falls into a supermassive black hole.

Known as AT2021lwx, the explosion has currently lasted more than three years, compared to most supernovae which are only visibly bright for a few months.

According to the study, it took place nearly eight billion light years away, when the universe was around six billion years old, and is still being detected by a network of telescopes.

The astronomers, led by the University of Southampton, believe the explosion is a result of a vast cloud of gas, possibly thousands of times larger than our sun, that has been violently disrupted by a supermassive black hole.

Fragments of the cloud would be swallowed up, sending shockwaves through its remnants, as well as into a large dusty “doughnut” surrounding the black hole.

Such events are very rare and nothing on this scale has been witnessed before, the researchers say.

Last year, astronomers witnessed the brightest explosion on record – a gamma-ray burst known as GRB 221009A..

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Although this was brighter than AT2021lwx, it lasted for just a fraction of the time, meaning the overall energy released by the AT2021lwx explosion was far greater.

AT2021lwx was first detected in 2020 by the Zwicky Transient Facility in California, and subsequently picked up by the Asteroid Terrestrial-impact Last Alert System (ATLAS) based in Hawaii.

But until now the scale of the explosion had been unknown.

Dr Philip Wiseman, research fellow at the University of Southampton, who led the research, said: “We came upon this by chance, as it was flagged by our search algorithm when we were searching for a type of supernova.

“Most supernovae and tidal disruption events only last for a couple of months before fading away. For something to be bright for two plus years was immediately very unusual.”

The Southampton-led team believe the most feasible explanation for what caused the explosion is an extremely large cloud of gas (mostly hydrogen) or dust that has come off course from its orbit around the black hole and been sent flying in.

Dr Wiseman added: “With new facilities, like the Vera Rubin Observatory’s Legacy Survey of Space and Time, coming online in the next few years, we are hoping to discover more events like this and learn more about them.

“It could be that these events, although extremely rare, are so energetic that they are key processes to how the centres of galaxies change over time.”

The findings are published in Monthly Notices of the Royal Astronomical Society.