Astronomers recently spotted the closest pair of supermassive black holes known to date, and the record has two meanings. They are not only the closest duo to Earth, but also the tightest pair ever detected.
Un double record
The two black holes are located in the galaxy NGC 7727, about 89 million light years from the Terre. It might sound like a long way off, but in cosmic terms it is just a stone’s throw away (previous record holders were 470 million light years away). Obviously, the black hole nearest supermassive remains Sagittarius A*, which is in the center of the Milky Way, just 26,000 light years from our planet.
But the proximity between the two supermassive black holes is perhaps even more intriguing. They are only 1,600 light years apart, less than half the distance seen for previous record holders, and they continue to get closer.
« The low separation and speed of the two black holes indicate that they will merge and form a single monstrous black hole, possibly within 250 million years. “, Explain Holger Baumgardt, co-author of the study, recently published in the journal Astronomy & Astrophysics.
Located in the heart of the galaxy, the largest has a mass approximately 154 million times that of the Soleil, when the second displays “only” 6.3 million solar masses on the scale. Researchers believe it was originally the nucleus of another galaxy that merged with NGC 7727 about a billion years ago.
Many hidden supermassive black holes
Such a collision had long been suspected. NGC 7727 is a very irregular galaxy, with amorphous spiral arms and strange star currents in its outer regions. The two bright objects near the center were thought to be supermassive black holes, but this had not been confirmed.
The authors of the study therefore set out to measure the mass of these objects. They used the Multi Unit Spectroscopic Explorer (MUSE), an instrument of Very Large Telescope (VLT) to Chili, to study the gravitational influence that objects exert on the stars which surround them. This study found that the objects had masses of several million suns, making supermassive black holes the only possible candidates.
« Our discovery implies that there may be many more of these galaxy fusion relics, and that they may contain many hidden massive black holes still waiting to be discovered. “, Explain Karina Voggel, lead author of the study. ” This could increase the total number of known supermassive black holes in the local Universe by 30%. »