Tidal interruption event: The star shattered by the black hole is one of the brightest things ever seen.

A star orbiting a supermassive black hole at the center of a distant galaxy was shattered in a tidal disruption event, the most distant event ever observed.


30 November 2022

An artist’s impression of a tidal disruption event created by a black hole swallowing a star

Carl Knox / OzGrav, ARC Center of Excellence for Gravitational Wave Discovery, Swinburne University of Technology

Astronomers have found the farthest known example of a star being eaten by a supermassive black hole, creating one of the brightest events ever seen in the universe.

When a star gets too close to a supermassive black hole at the center of a galaxy like ours, it can break apart and be dragged into a disk surrounding the black hole; this is an energetic ordeal known as a tidal disruption event. Astronomers have seen about 70 of these events to date.

In February, researchers at Palomar Observatory in California detected a new, extremely bright tidal disruption event they named AT2022cmc. Follow-up observations by telescopes around the world revealed that it took place in a galaxy about 12.5 billion light-years away from us. “This is a new record,” says Igor Andreoni of the University of Maryland. “The most distant tidal disturbance event ever discovered.”

This distant destruction was only visible because the black hole ejected a blast of plasma and radiation from its poles at close to the speed of light as it devoured the star; this was a rare event thought to occur in only 1 percent of tidal disruption events. Andreoni says this jet was pointed directly at us, making the AT2022cmc one of the “brightest” astronomical events ever observed. It is not fully understood how these jets are produced. “It’s still a mystery,” says Andreoni.

Further analysis of the AT2022cmc can tell us more. While the star eaten by the black hole was similar to our sun in size and mass, the black hole that produced it was similar to the central black hole of the Milky Way, but of relatively low mass as dwarfed by those in other galaxies. Andreoni says the black hole also appears to be spinning at a fast rate, which could be important for jet generation. “Black holes spinning very fast could be the key,” he says.

Journal reference: NatureDOI: 10.1038/s41586-022-05465-8, Nature AstronomyDOI: 10.1038/s41550-022-01820-x

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