Astronomers readily admit that black holes are hard to find – even the supermassive ones. Knowing that most galaxies have a supermassive black hole in their center helps, but some that formed when two galaxies collided should have a pair of supermassive black holes that gravitate together in a gravitational hug. That was the case with the galaxy NGC 7727, in the constellation Aquarius, whose peculiar irregular shape indicated a collision, but it was only recently that astronomers using the using the European Southern Observatory (ESO) Very Large Telescope (VLT) discovered its two supermassive black holes … and were immediately in a frenzy when they realized they were the closest pair of supermassive black holes to Earth ever detected and so close to each other that their hug looks more like a dance of death.
“The small separation and velocity of the two black holes indicate that they will merge into one monster black hole, probably within the next 250 million years.”
That’s the blink of a cosmic eye, according to Holger Baumgardt, a professor at the University of Queensland and co-author of a study published in the journal Astronomy & Astrophysics which announced the discovery of two tightly joined supermassive black holes just 89 million light-years from Earth and only 1600 light-years apart – dead-center in the galaxy GC 7727. The larger one has a mass almost 154 million solar masses, while the smaller is 6.3 million solar masses. Together, they affect the motion of the stars around them and that’s how Karina Voggel, an astronomer at the Strasbourg Observatory in France and lead author of the study, found them.
“Our finding implies that there might be many more of these relics of galaxy mergers out there and they may contain many hidden massive black holes that still wait to be found. It could increase the total number of supermassive black holes known in the local Universe by 30 percent.”
One of them might be NGC 7252, a neighbor of NGC 7727 in the Aquarius constellation located 220 million light years away that may have two supermassive black holes or one intermediate-mass black hole. These merged galaxies are generally extremely old and can help understand the early days of the universe when they were two separate galaxies.
Sadly, we also know the not-too-distant future of these dancing supermassive black holes – a supermassive collision resulting in one survivor … possibly a mysterious intermediate black hole which astronomers suspect are the result of such mergers. While it’s only 250 million years away, we’re going to miss it.
Since it won’t be on pay-per-view, photos of the dancing supermassive black holes can be seen here. Bets on what will happen can probably be placed in Vegas.