NASA simulates two supermassive black holes spiraling toward a collision

The physics of supermassive black holes is difficult to understand even for scientists who devote their lives to studying such objects. When you add a second black hole, things become even more difficult to follow. Scientists have never been able to observe the collision of two black holes, but a new simulation of NASA's Goddard Space Flight Center could clear up physics.

It is well established at this point that large galaxies have supermassive black holes in the center. We also know that the galaxies of the universe are fusing regularly. Yet we see very few galaxies with two giant black holes in the center. Those we see are not close enough for their gravitational fields to interact, which makes it difficult to identify the fusion of black holes from light alone. We do not know what to look for, but the new Goddard simulation might help.

Gravitational waves from the fusion of smaller black holes have been confirmed with instruments such as the National Science Foundation's Gravitational Laser Interferometer Observatory (LIGO). A fusion of supermassive black holes would be much more distant, so we can not rely on gravitational waves to locate them. The Earth is too noisy to pick up the signal. We know something about gas emissions in orbit around supermassive black holes, and that's where the Goddard researchers focused their attention.

Supermassive black holes should result in overheated gas clouds as they melt, and even more gas would end up around a black hole if two galaxies merged. The researchers modeled three supermassive black holes in orbit three times to determine the behavior of this gas shortly before a collision. They found that this stage of the process would be dominated by intense UV and X gas emissions in three distinct regions. There would be a ring of colder gas around the pair of black holes, as well as smaller, warmer discs surrounding each singularity. A stream of gas would also feed the smaller discs of the surrounding halo.

As the material enters the black holes, the simulation predicts that UV light will interact with the black hole crown to produce higher X-ray emissions. With a lower rate, the UV light would drop. Scientists expect X-ray emissions from a pair of fusing black holes to be much brighter than either could produce alone.

It took the Blue Waters Supercomputer 46 days to produce this simulation with its 9,600 processor cores, and it is not even complete. NASA did not attempt to model the center of gravity between the two masses in orbit. It's just a black circle in the animation. There is still a lot to learn.

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