We saw a black hole rip apart a star 8.5 billion light-years away

A black hole engulfing a star has been identified as 8.5 billion light-years from Earth. This is the most distant detection of this type of cataclysmic event.

Stars that roam too close to black holes are very reckless. They usually end up torn apart by the extreme gravity of black holes, which readily gobble up this material. We have just detected the most distant of these events, announces the European Southern Observatory (ESO) on November 30, 2022. The detection is detailed in the journal Nature.

The observed event is named AT2022cmc. The light it produced began its journey to us when the Universe was only a third of its current age (14 billion years). The source of this rare phenomenon is estimated to be 8.5 billion light-years from Earth. It lies at the center of its host galaxy. It is a supermassive black hole, which expelled the remnants of the devoured star in a jet of matter moving at near the speed of light.

Artist’s impression of the AT2022cmc event. // Source: Carl Knox – OzGrav, ARC Center of Excellence for Gravitational Wave Discovery, Swinburne University of Technology

A tidal rupture event, or when a black hole swallows a star

We also speak of a tidal rupture event to describe this type of cataclysm, the scientists recall in their study. Tidal rupture events are bursts of electromagnetic energy released when supermassive black holes at the center of galaxies violently disrupt a passing star. It’s a bit like squeezing a tube of toothpaste in the middle. Material is ejected from the ends. It is a comparable phenomenon but at the level of the two poles of the rotating black hole.

The study of this source was made possible by several observatories and by the coordination of various research teams. AT2022cmc was first detected on February 11, 2022, as part of the Zwicky Transient Facility, an astronomical survey mobilizing a telescope from the Palomar Observatory (California). Faced with this atypical event, other observations were quickly organized. Thus, it is thanks to the Noema radio telescope, located in the Alps, that the source could be characterized. As for the Very Large Telescope of ESO, from the Cerro Paranal Observatory in Chile, it has the identity of the origin of AT2022cmc.

Soon, the James Webb Telescope will also observe this source

The analyzes are not complete. The Hubble and James Webb space telescopes are also expected to help study this source. This will only be possible when the light intensity of the material jet has been reduced.

This detection is important because researchers do not yet know why all encounters between black holes and stars do not systematically emit jets of matter. Only 1% of tidal rupture events cause the ejection of plasma jets, recalls the ESO. One hypothesis considered is based on the rotation of black holes: it would be those that rotate the fastest on themselves that would be able to feed such bright jets.

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