Only 89 million light-years away, in the galaxy NGC 7727, two supermassive black holes She is destined to become one.
New measurements that have investigated the galaxy’s core find that the core consists of a pair of supermassive black holes. It’s the closest pair we’ve discovered so far, beating the previous record holder of 470 million light-years away by a large margin.
Furthermore, the two supermassive black holes are closer to each other than any other supermassive black hole binary we’ve seen, separated by only 1,600 light-years. Eventually, astronomers believe, the two black holes will grow so close to each other that they will merge, becoming a much larger monster.
Not only does the discovery confirm that NGC 7727 is the product of a merger between two galaxies, but it gives us a wonderfully close laboratory to investigate interactions between supermassive black holes as they spin in an orbital pre-merger dance.
“This is the first time we’ve found two supermassive black holes so close together, less than half the distance between the previous record holder,” Astronomer Karina Vogel says: From the Strasbourg Observatory in France.
There are many reasons why supermassive black hole binaries are of interest to astronomers. Supermassive black holes are found at the centers of most galaxies, the nuclei around which everything else orbits.
When two galaxies are found together, it indicates that two galaxies have come together. We know this process is happening; Finding a massive black hole binary could tell us what it looks like in the final stages.
Supermassive black hole binaries can also tell us something about how these massive objects – millions to billions of times the mass of the Sun – can become so incredibly massive. A binary black hole merger is one way this growth can occur. Finding supermassive black holes will help us understand if this is a common path for this growth, which in turn will allow for more accurate modeling.
NGC 7727 has been an interesting target for a binary supermassive black hole for some time. Its physical properties suggest that the galaxy is the product of a galactic merger, sometime in its distant past. However, black holes are hard to see unless they are actively accumulating material. Then, the cloud of material around the black hole shines brightly. NGC 7727 did not have the bright flux normally associated with active supermassive black holes.
This is where the proximity of the galaxy gave astronomers an advantage. Because NGC 7727 is so close, the researchers were able to obtain motion data for the stars in the galactic center, based on the way their light changes as they rotate. This revealed that the galactic center contains not one, but two supermassive black holes.
One of those supermassive black holes is relatively large, with a mass about 154 million times the mass of the Sun. The other companion, much smaller, is only 6.3 million solar masses. Only one of these black holes has been found to be active: the smallest. This explains the reason for the lack of radiation. The larger black hole is quiet.
This suggests that there could be many more supermassive black hole binaries than we can currently detect, the researchers said.
“Our discovery indicates that there may be a lot of remnants of galactic mergers, and they may contain many hidden massive black holes still waiting to be found,” Vogel said.
“The total number of known supermassive black holes in the local universe could increase by 30%.”
Although the two black holes are destined to merge, it will take some time; The researchers said that about 250 million years or so. But, while we won’t be able to notice this happening, the binary system offers hope that there are many supermassive black hole mergers happening all around us.
We cannot discover them yet; The gravitational waves emitted would be of a very low frequency for our current devices. But new tools like space gravity wave The LISA reagent, the researchers said, should be able to.
And this discovery could tell us how to find supermassive binary black holes, even in distant galaxies, where we can’t get detailed motion data for central stars.
“Targeting bright nuclear star clusters remaining in compact galaxies could facilitate detection of supermassive black holes at smaller intervals in the local universe even when active galactic cores are not luminous,” They wrote in their paper.
“This will allow for more detailed studies of these systems which can serve as blueprints for how to find them on a larger scale in the distant universe.”
The search was published in Astronomy and astrophysics.