Astronomers have discovered three black holes orbiting each other
black hole from interstellar Interstellar Movie
- For the first time, researchers have been able to observe three supermassive black holes orbiting around each other.
- The third black hole could be the key to a big problem of theoretical physics.
- The method used by the researchers could be used to find more threesomes
At the core of every galaxy is a supermassive black hole. How exactly they are formed, we do not know yet. A research team may now have come a little closer to the puzzle. They discovered for the first time three black holes in the center of three colliding galaxies that are in the process of merging, as they described in the study published in the Astrophysical Journal appeared.
When galaxies collide, there is actually less collision than one would expect. Due to the huge empty spaces between the stars, collisions rarely occur. But what is sure: The galactic nuclei, i.e. the supermassive black holes of the different galaxies, must merge.
Researchers may have solved an important problem in physics
The results of these death dances we observe also in the reality: There exist black holes with so enormous masses that they can have originated only by such fusion processes. They often have a mass millions or billions of times that of the sun. We have also observed such an event indirectly before, when one of the predictions of Albert Einstein’s theory of relativity was confirmed in 2015- Gravitational Waves. They echo through the universe when black holes merge. Meanwhile, researchers encounter colliding black holes about once a week while studying gravitational waves.
In physical theory, however, we don’t yet understand how this can happen at all. When two black holes approach each other, their incredibly high specific orbital energies should prevent them from merging. They could approach only up to a few light-years, then the merging process would have to stop, because no more objects are left in the environment to which they could give away their energy. This problem is called the "Final Parsec Problem" in physics.“
The study’s authors believe they may have found a solution: A third black hole, like the one in this system, that ensures black holes can merge after all. The specific orbital energy of the merging black holes could be given to the accompanying third black hole, so that a merger can take place after all. A computer simulation already showed that 16 percent of black hole pairs in colliding galaxies come into contact with another supermassive black hole before they merge, researchers say.
It takes several telescopes to detect such triplets
„This is the strongest evidence we have yet found that such triple systems are actively feeding supermassive black holes", Study leader Ryan Pfeifle, of George Mason University in Fairfax, Virginia, said.
Such systems are extremely difficult to detect because there is a lot going on around them. Gas and dust often rob researchers of a direct view of such events. For this study, several telescopes were used to scan different parts of the electromagnetic spectrum- about visible light and X-rays. „We were only looking for pairs of black holes, but through our search method we have stumbled upon this fascinating system", so Pfeifle.
„By using these large observatories, we have found a new way to identify triple black holes. Each telescope gives us a different indication of what’s really going on in the system", so Pfeifle. The Sloan Digital Sky Survey telescopes in the U.S. state of New Mexico, and the Chandra and Wide-Field Infrared Survey Explorer space telescopes contributed to the discovery. „We hope to expand our work by finding more systems of three using the same technique", says Pfeifle.