Science

Astronomers Capture Black Hole Swallowing Star In ‘Hyper-Feeding Moon’

Astronomers Capture Black Hole Swallowing Star In ‘Hyper-Feeding Moon’

Increase / Illustration of a star being spaghettized as it was sucked in by a tidal supermassive black hole (TDE).

ESO/M. Grain fairs

Earlier this year, astronomers caught an unusually bright signal in the X-ray, optical and radio modes, called AT 2022cmc. They have now determined that the most likely source of that signal is a supermassive black hole that is devouring the star in a “hyper-feeding frenzy,” releasing jets of matter in what’s known as a tidal event (TDE). According to new paper published in the journal Nature Astronomy, is one for the record books: the the most distant such event yet discovered approximately 8.5 billion light years from us.

The authors estimate that the jet from this TDE is traveling at 99.99 percent the speed of light, meaning the black hole is indeed chomping on its stellar meal. “It is probably devouring the star at a rate of half the mass of the Sun per year,” said co-author Dheeraj “DJ” Pasham University of Birmingham. “Many tidal disruptions happen early, and we were able to catch this event right at the beginning, within a week of the black hole starting to feed on the star.”

Like us published earlierit is a popular misconception that black holes behave like cosmic vacuum cleaners, they voraciously suck up any matter in their environment. 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 the matter of an object is ejected in a powerful jet.

If that object is a star, the process of shredding (or “spaghetti”) by the strong gravitational forces of the black hole occurs outside the event horizon, and part of the star’s original mass is violently ejected outwards. This in turn can be formed a rotating ring of matter (aka an accretion disk) around a 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 clamped tightly around the middle” so that matter sprays out at both ends. TDEs are one way astronomers can indirectly infer the presence of a black hole.

For example, astronomers published in 2018 first direct image about the aftermath of a star ripped apart 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 final death throes star that was ripped apart by a supermassive black hole, called AT 2019qiz, which provided the first direct evidence that gas outflow during disruption and accretion produces the powerful optical and radio emissions previously observed. In January, astronomers spotted another radio TDE candidate (named J1533+2727) in archival data collected by the Very Large Array (VLA) telescope in New Mexico.

A black hole devours a star that got too close.  In very rare circumstances, this can also result in jets moving at nearly the speed of light that create the light our telescopes observe at many frequencies.  AT2022cmc is the most distant such event recorded to date.
Increase / A black hole devours a star that got too close. In very rare circumstances, this can also result in jets moving at nearly the speed of light that create the light our telescopes observe at many frequencies. AT2022cmc is the most distant such event recorded to date.

Zwicky Transient Facility/R. Hurt (Caltech/IPAC)

Astronomers first spotted AT 2022 cmc in February i immediately turned multiple telescopes operating in a wide range of wavelengths towards the source. This included an X-ray telescope on the International Space Station called the Neutron Star Interior Composition Explorer (NICER). It is possible that the bright signal – calculated to be equivalent to the light of 1,000 trillion suns – was gamma radiation 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 that the source is hot: about 30,000 degrees, which is typical of TDEs,” said co-author Matt Nicholl University of Birmingham. “But we also saw some absorption of light by the galaxy where this event occurred. These absorption lines were strongly redshifted, which tells us that this galaxy is much further away 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 indicated an “extreme enlargement episode”. A vortex of debris then forms as the unlucky star falls into the black hole. But the glow was still a surprise, given how far the source is from Earth. The authors attribute this to so-called “Doppler amplification,” which occurs when the jet points directly toward Earth, similar to how the sound of a passing siren is amplified. AT 2022cmc is only the fourth Doppler-enhanced TDE yet found; the last one was discovered in 2011.

A black hole more than halfway across the universe ejects matter at close to the speed of light.

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



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