Astronomers capture black hole engulfing star in ‘hyper-feeding frenzy’

Earlier this year, astronomers picked up an unusually bright signal in the X-ray, optical and radio regimes, dubbed AT 2022cmc. They have now determined that the most likely source of this signal is a supermassive black hole engulfing a star in a “hyper-feeding frenzy”, shooting out jets of material in what is called a tidal disturbance event ( TDE). According to a new article published in the journal Nature Astronomy, it is one of the records: the most distant event of its type ever detected at around 8.5 billion light years.

The authors estimate that the jet from this TDE is traveling at 99.99% of the speed of light, which means the black hole is really swallowing its stellar meal. “It’s probably swallowing the star at the rate of half the mass of the Sun per year,” said co-author Dheeraj “DJ” Pasham of the University of Birmingham. “A lot of this tidal disturbance happens very early on, and we were able to capture this event early on, within a week of the black hole starting to feed on the star.”

As we reported earlier, it’s a common misconception that black holes behave like cosmic vacuum cleaners, voraciously sucking up any matter in their surroundings. In reality, only things that pass beyond the event horizon, including light, are swallowed up and cannot escape, although black holes are also messy eaters. This means that part of an object’s material is ejected in a powerful jet.

If this object is a star, the process of being shredded (or “spaghettified”) by the powerful gravitational forces of a black hole occurs outside the event horizon, and some of the original mass of the star is violently ejected outwards. This, in turn, can form a spinning ring of matter (aka an accretion disk) around the black hole that emits powerful X-rays and visible light, and sometimes radio waves. Physicist John Wheeler once described jet TDEs as “a tube of toothpaste squeezed down the middle”, so that matter shoots out at each end. TDEs are a way for astronomers to indirectly infer the presence of a black hole.

For example, in 2018, astronomers announced the first direct image of the aftermath of a star being shredded by a black hole 20 million times more massive than our Sun in a pair of colliding galaxies called Arp 299, about 150 million away. light years from Earth. . A year later, astronomers recorded the final agony of a star being shredded by a supermassive black hole, dubbed AT 2019qiz, which provided the first direct evidence that gas escaping during disruption and accretion produces the powerful emissions optical and radio previously observed. In January, astronomers spotted a second TDE candidate in the radio regime (dubbed J1533+2727) in archival data collected by the Very Large Array (VLA) telescope in New Mexico.

Astronomers first spotted AT 2022cmc in February and quickly slew several telescopes operating at a wide range of wavelengths toward the source. These included an X-ray telescope aboard the International Space Station called the Neutron Star Interior Composition Explorer (NICER). It was possible that the light signal – calculated as equivalent to the light from 1,000 trillion suns – was a gamma-ray burst from the collapse of a massive star. But the data revealed a source 100 times more powerful than even the strongest known gamma-ray burst.

“Our spectrum told us the source was hot: around 30,000 degrees, which is typical for a TDE,” said co-author Matt Nicholl from the University of Birmingham. “But we also saw some absorption of light by the galaxy where this event took place. These absorption lines were strongly shifted to redder wavelengths, telling us that this galaxy was much further away than expected.

Given AT 2022cmc’s brightness and longer duration, astronomers concluded that it must be powered by a supermassive black hole. X-ray data also indicated an “extreme accretionary episode”. That’s when a whirlwind of debris forms as the unfortunate star falls into the black hole. But the brightness was still a surprise, given the source’s distance from Earth. The authors attribute this to something called “Doppler boosting”, which occurs when the jet points directly at Earth, much like the way the sound of a passing siren is amplified. AT 2022cmc is only the fourth Doppler-boosted TDE to date; the last was detected in 2011.

DOI: Nature Astronomy, 2022. 10.1038/s41550-022-01820-x (About DOIs).