Scientists stumped after black hole 'burps' up star years after 'eating' it

Astronomers have been left scratching their heads after a supermassive black hole essentially 'burped' up a star that it had 'eaten' three years ago.

Back in 2018, scientists witnessed a small star in a galaxy 665 million light years away from Earth get torn to shreds when it got a little too close to a black hole - which, at the time, was nothing out of the ordinary.

But nearly three years ago, in June 2021, astronomers were caught 'completely by surprise' when that same black hole lit up the skies by spitting out stellar matter.

This was particularly strange to experts, since the black hole hadn't swallowed anything new since its 2018 feast.

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“This caught us completely by surprise — no one has ever seen anything like this before,” said Yvette Cendes, the lead author of a new study analysing the phenomenon.

The results of Dr Cendes's study, published in the Astrophysical Journal this week, suggested that the black hole was now regurgitating stellar matter at half of the speed of light - though they still can't figure out why there was delay of almost three years.

“It’s as if this black hole has started abruptly burping out a bunch of material from the star it ate years ago," said Dr Cendes.

A black hole, according to NASA, as a place in space where gravity pulls so much that even light can't get out. They're usually formed from the remnants of large dying stars, or supernovas.

Edo Berger, a professor of astronomy at Harvard University and co-author of this new study, noted that his team have been studying tidal disruption events (TDEs) for decades, and it's quite common for them to spew out material when a star is being consumed by a black hole.

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“But in AT2018hyz [the black hole in this new study] there was radio silence for the first three years, and now it’s dramatically lit up to become one of the most radio luminous TDEs ever observed."

He added that this was the first time they had seen 'such a long delay between the feeding and the outflow'.

Not only that, but the stellar material being 'burped' out is travelling at 50 percent the speed of light, which is also pretty unusual.

Typically, when TDEs spit out matter, it travels at 10 percent the speed of light.

Now, the team plan to investigate "whether this actually happens more regularly and we have simply not been looking at TDEs late enough in their evolution.”

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