Astronomers from Queen's University Belfast have helped discover a cosmic explosion that is 10 times brighter than any known supernova (exploding star).

The investigation was led by led by Dr Philip Wiseman, a research fellow at the University of Southampton, in collaboration with Queen’s University Belfast. Researchers uncovered the explosion using the Asteroid Terrestrial-impact Last Alert System (Atlas).

Atlas first spotted the explosion, named AT2021lwx, back in November 2020 and has been observing it every few nights for the last 2½ years.

"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.

Most supernovae are only visibly bright for several months, but AT2021lwx has lasted more than three years. The last one visible in our galaxy was seen from Earth in 1605. Data shows that the event causing this explosion occurred long before the Sun or Earth formed.

Following a detailed analysis, the astronomers believe the explosion is a result of a vast cloud of gas that has been violently disrupted by a supermassive black hole. This cloud of gas was possibly thousands of times larger than our sun.

Matt Nicholl from Queen’s helped to analyse the brightness of the explosion. He described the discovery as “totally unprecedented.”

“At first, we thought this flare-up could be the result of 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,” said Dr Nicholl.

If an event like this were to occur in our galaxy or our neighbouring galaxies, it would be so bright as to be visible during day time. Astronomers believe these types of black holes lie in the centre of virtually all large galaxies.

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.