Light in the sky caused by star 'squeezed' by black hole

Artist's impression of a star being squeezed by the intense gravitational pull of the black hole

An "extraordinary flash" seen in the sky earlier this year was caused by a distant star being "squeezed like a toothpaste tube" by a supermassive black hole, astronomers have said.

The star got too close to the black hole, sparking a light show brighter than a thousand trillion suns. The tidal disruption event (TDE), which is when a star is ripped apart by a black hole's tidal forces, was so bright it could be detected by instruments on Earth.

Although TDEs have been seen before, experts say this one, called AT2022cmc is the brightest yet!

At more than eight billion light-years away, it is also the farthest TDE ever detected, more than halfway across the universe.

The scientists said their findings, published in two papers in the journals Nature and Nature Astronomy, could help explain how supermassive black holes feed and grow.

Dr Matteo Lucchini, a postdoc researcher at the MIT Kavli Institute for Astrophysics and Space Research in the US, and one of the authors on the Nature Astronomy paper, said: "We know there is one supermassive black hole per galaxy, and they formed very quickly in the universe's first million years.

"That tells us they feed very fast, though we don't know how that feeding process works.

"So, sources like a TDE can actually be a really good probe for how that process happens."

Dr Daniel Perley, a reader in astrophysics at Liverpool John Moores University, who is one of the authors on the Nature paper, said that AT2022cmc was an "extraordinary" type of TDE.

He said: "The most known types of explosions are either much faster, much slower, or much bluer in colour than inferred from the data.

"Usually, intense gravitational forces tear the star apart…

"However, in this case, something happened that ejected matter almost at the speed of light back into space.

"The way we describe it is as a toothpaste tube being squeezed suddenly in the middle causing the contents to squirt matter out of both ends.

"Then, as the material collides with surrounding gas, the intense optical, radio, and X-ray emission is produced."

The remains of the squeezed star created a powerful jet, resulting in what scientists say was an "extraordinary flash" detected by the team at the Zwicky Transient Facility in California during a routine all-sky survey in February.

Artist's impression of a tidal disruption event where a star is being torn apart by a supermassive black hole

Experts believe this luminous jet was pointing directly toward Earth, which meant instruments and telescopes could record the event in detail.

Astronomers say TDEs such as AT2022cmc are rare - the last time scientists discovered one of these jets was more than ten years ago.

Multiple instruments from across the globe, including the Liverpool Telescope in Spain and European Southern Observatory's Very Large Telescope in Chile, were used to learn more about the event.

Analysis showed that AT2022cmc was hot - around 30,000 degrees - which is typical for a TDE, according to astronomers.

However, it is still a mystery why some TDEs launch jets while others do not.

As more powerful telescopes are launched, astronomers say they may be able to observe more TDEs and get some answers.

Dr Lucchini said: "We expect many more of these TDEs in the future.

"Then we might be able to say, finally, how exactly black holes launch these extremely powerful jets."