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

Earlier this year, astronomers caught an unusually bright signal in the X-ray, optical and radio regimes, called AT 2022cmc. They have now determined that the most likely source of this signal is a supermassive black hole devouring a star in a “hyper-feeding frenzy,” shooting out jets of matter in what’s known as a tidal disruption event ( TDE). Seconds a new role published in the journal Nature Astronomy, is one of the record books: the more distant this event it has yet to be detected about 8.5 billion light years away.

The authors estimate that the jet from this TDE is traveling at 99.99 percent of the speed of light, meaning the black hole is actually consuming its stellar food. “The star is probably being swallowed up at a rate of half the mass of the Sun per year,” said co-author Dheeraj “DJ” Pasham from the University of Birmingham. “A lot of this tidal disruption happens early on, and we were able to catch this event right at the beginning, a week after the black hole started feeding on the star.”

As we did previously reportedit’s a popular misconception that black holes behave like cosmic vacuum cleaners, voraciously sucking in any matter from its environment. Actually, only things beyond the event horizon, including light, get swallowed up and can’t escape, although black holes are also messy eaters. This means that part of the matter of an object 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 star’s original mass is violently expelled outwards. This, in turn, can be formed a spinning ring of matter (also known as 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 held tight in the middle,” so that matter comes out at either end. TDEs are one way astronomers can indirectly infer the presence of a black hole.

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

Astronomers first detected at 2022cmc in February and he quickly turned around multiple telescopes operating over a wide range of wavelengths towards the source. These include an X-ray telescope aboard the International Space Station called the Neutron Star Interior Composition Explorer (NICER). It was possible that the bright signal—calculated to be equivalent to the light of 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 gamma-ray burst known.

“Our spectrum told us that the source was hot: around 30,000 degrees, which is typical of 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 occurred. These absorption lines were greatly shifted to redder wavelengths, which told us that this galaxy was very farther than we expected.”

Given the brightness of AT 2022cmc and its longer duration, astronomers concluded that it must be powered by a supermassive black hole. The X-ray data also pointed to an “extreme accretion episode”. That’s when a whirlwind of debris forms as the unlucky 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 a so-called “Doppler boost,” which occurs when the beam points directly toward Earth, in the same way that the sound of a passing siren is amplified. AT 2022cmc is only the fourth Doppler-enhanced TDE yet found; the last one was detected in 2011.

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