Pair of supermassive black holes to merge into one mega black hole

In the heart of almost all galaxies, including ours, is a monstrously large black hole with a mass millions or billions of times that of the sun. These supermassive black holes are generally lonely beasts, but astronomers have recently discovered the closest pair of them that will eventually merge into an even larger black hole.

The galaxy NCG 7727 is home to the pair of black holes, which is located about 89 million light-years distant from Earth, much closer than the closest pair previously recorded, which is 470 million light-years away. The recently discovered pair is very close to each other by black hole standards, at a distance of 1,600 light-years, and is believed to have been joined by the merger of two galaxies.

“It is the first time that we have found two supermassive black holes that are so close to each other, less than half the separation of the previous record holder,” said lead author Karina Voggel, an astronomer at the Strasbourg Observatory in France. The team detected the pair using the Multiple Unit Spectroscopic Explorer (MUSE) instrument on the European Southern Observatory’s Very Large Telescope, which was able to measure the masses of the two black holes by observing how they affected the movements of stars around them.

They found that the largest of the black holes has a mass 150 million times that of the sun, and its smallest companion has a mass 6.3 million times that of the sun. The fact that the two are so close together (relatively speaking) means that they are likely to merge in the future.

“The small separation and speed of the two black holes indicate that they will merge into a monstrous black hole, probably within the next 250 million years,” said co-author Holger Baumgardt, a professor at the University of Queensland, Australia.

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