Galactic clash strips stars from supermassive black hole

A “nearly naked” supermassive black hole, stripped of its galaxy, has been found fleeing the scene of a collision.

Astronomers using the National Science Foundation’s Very Long Baseline Array examined a cluster of galaxies more than two billion light-years from Earth, and found evidence of a close encounter between two galaxies – and the consequences of this. 

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The encounter millions of years ago stripped the smaller galaxy of almost all its stars and gas.

This left only its black hole and the remnants of the galaxy, now only about 3,000 light-years across – our galaxy, by comparison, is about 100,000 light years across.

Supermassive black holes are thought to be found at the centre of most galaxies, and are millions or billions of times the mass of the sun.

Large galaxies, astronomers suspect, grow by consuming smaller ones. In these situations, each galaxy’s central black hole is expected to orbit the other and eventually merge. 

This research which is accepted for publication in The Astrophysical Journal, intended to find orbiting pairs of supermassive black holes – evidence of a galaxy merger. 

“Instead, we found this black hole fleeing from the larger galaxy and leaving a trail of debris behind it,” says study co-author James Condon from the National Radio Astronomy Observatory in the US.

The video above explains how this nearly-naked supermassive black hole was found and what it means for future research into the evolution of galaxies. 

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An artist’s conception of how the ‘nearly naked’ supermassive black hole came to be.
Bill Saxton, NRAO / AUI / NSF

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