Caught in the act: supermassive black hole 8.5 billion light years away enjoys violent stellar snack
A supermassive black hole at the centre of a galaxy some 8.5 billion years way has ripped apart a nearby star, producing some of the most luminous jets ever seen.When stars and other objects stray too close to a supermassive black hole they are destroyed by the black hole’s immense gravity.
These occurrences, known as tidal-disruption events (TDEs), result in a circling disk of material that is slowly pulled into the black hole and very occasionally, as in the case of supermassive black hole AT2022cmc, ejecting bright beams of material travelling close to the speed of light.
The Cerro Paranal mountain top is home to the world’s most advanced ground-based facility for astronomy, hosting the four 8.2-metre Unit Telescopes of the Very Large Telescope. Credit: ESO/G. Hüdepohl
Luminous jets are produced in an estimated 1% of cases and are known as a type of astronomical occurrence known as a transient, because they are short-lived.
Bright flashes from the jets were spotted in data from the Zwicky Transient Facility (ZTF) in February this year using a special new technique which can comb through the equivalent of a million pages of information every night.
Due to the rapid results produced by the novel data analysis method, a research team in the US was able to swiftly follow up on the transient event with multiwavelength observations of the system from different observatory facilities.
The jets were visible across many wavelengths, from X-rays to radio, and follow-up observations enabled the European Southern Observatory’s Very Large Telescope to place AT2022cmc at a whopping distance of 8.5 billion light years away, while optical and infrared observation from NASA’s Hubble telescope were able to precisely pinpoint AT2022cmc’s location.
“The last time scientists discovered one of these jets was well over a decade ago,” said Michael Coughlin, an assistant professor of astronomy at the University of Minnesota Twin Cities and co-lead on the paper published in Nature. “From the data we have, we can estimate that relativistic jets are launched in only 1% of these destructive events, making AT2022cmc an extremely rare occurrence.”
Exactly why this behaviour is so rare remains an enigma, however, the research team believe that AT2022cmc’s rapid spin powers the jets, adding to the current understanding of the physics of these behemoth dead stars at the centres of galaxies.
A black hole devours a star that has come too close. In very rare circumstances, this may also result in jets moving with almost the speed of light that generate light observed by our telescopes at many frequencies. AT2022cmc is the most distant such event recorded to date. Credit: Zwicky Transient Facility/R. Hurt (Caltech/IPAC)
This detection – and the method used to discover it – are valuable as a future models for astronomers as they scour the skies for more events. “Scientists can use AT2022cmc as a model for what to look for and find more disruptive events from distant black holes,” says lead author Igor Andreoni, from the Department of Astronomy at UMD and NASA Goddard Space Flight Centre.
This includes using ground-based optical surveys, as opposed to gamma-ray observatories in space – how previous jets were primarily discovered.
“Our new search technique helps us to quickly identify rare cosmic events in the ZTF survey data,” says Andreoni.
“And since ZTF and upcoming larger surveys such as Vera Rubin’s Large Synoptic Survey Telescope scan the sky so frequently, we can now expect to uncover a wealth of rare, or previously undiscovered cosmic events and study them in detail. More than ever, big data mining is an important tool to advance our knowledge of the universe”.
