Star ‘squeezed like toothpaste tube’ by supermassive black hole in cosmic show

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.

In what experts describe as one of the most violent events in the universe, the unlucky star met its fate after wandering too close to this black hole, sparking a light show bright enough – with more light than a thousand trillion suns – to be detected by instruments on Earth.

Astronomers have previously observed other such tidal disruption events (TDEs) – where a passing star is ripped apart by a black hole’s tidal forces – but the experts say this one, dubbed AT2022cmc, is the brightest yet.

Occurring 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 shed new light on how supermassive black holes feed and grow.

Emissions from a tidal disruption event
Optical, radio, and X-ray emissions produced after a tidal disruption event (Zwicky Transient Facility/R Hurt/Caltech/IPAC)

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 that “didn’t seem to match any known type of celestial source”.

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, transforming it into a superheated disk of gas which eventually disappears into the black hole.

“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 debris from 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.

Experts believe this luminous jet was pointing directly toward Earth, allowing instruments and telescopes to record this event in detail.

Dr Dheeraj Pasham, also from the MIT Kavli Institute for Astrophysics and Space Research, who is the first author on the Nature Astronomy paper, said this team were able to “catch this event right at the beginning, within one week of the black hole starting to feed on the star”.

Astronomers say TDEs such as AT2022cmc are rare – the last time scientists discovered one of these jets was well over a decade ago.

A star being squeezed by the intense gravitational pull of the black hole
A star being squeezed by the intense gravitational pull of the black hole (ESO/M Kornmesser)

It is also the first time a “jetted TDE” jet has been detected during an optical survey.

Dr Perley said: “Until now, the small number of jetted-TDEs that are known were initially detected using high energy gamma-ray and X-ray telescopes.”

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.”

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