Supermassive black holes have been found at the center of almost every galaxy. They are gargantuan objects millions, if not billions, of times the mass of the Sun. Sometimes they merge with other supermassive black holes, a process so extreme it continues to challenge our theories, but we are yet to observe it.
New simulations have now been employed to better understand the spiraling of the black holes before they merge, and see if they produce any telltale features that might help us spot them in the future.
As reported in the Astrophysical Journal, this new model looks at what kind of light emission we could expect to see as the black holes circle each other before the collision, and whether this could help us to recognize the signs of an upcoming merger.
“Modeling these events requires sophisticated computational tools that include all the physical effects produced by two supermassive black holes orbiting each other at a fraction of the speed of light," explained co-author Manuela Campanelli, who initiated this project nine years ago. "Knowing what light signals to expect from these events will help modern observations identify them. Modeling and observations will then feed into each other, helping us better understand what is happening at the hearts of most galaxies.”
The simulations, made into a mesmerizing movie, shows how the light-emitting gas surrounding the black holes gets hotter and how the gravity of the black holes warps space-time. The light moving around the black holes gets lensed and magnified, glowing predominantly in ultraviolet and X-ray light.
Based on these simulations, researchers think that it could be possible to spot a merger before it happens as ultraviolet and X-ray emissions from a pair of supermassive black holes should be more variable and brighter than what we see from a single one. We have not yet observed light from regular black hole mergers either, however, but we have observed gravitational waves.
Unfortunately, our current gravitational wave observatories are not sensitive enough to spot gravitational emissions from supermassive black holes. Future ones will be though.
“The pairs [of supermassive black holes] we do see aren’t emitting strong gravitational-wave signals because they’re too far away from each other," said Scott Noble, an astrophysicist at NASA’s Goddard Space Flight Center. "Our goal is to identify — with light alone — even closer pairs from which gravitational-wave signals may be detected in the future.”
The team is now planning to refine this simulation allow for distance, masses, temperature and how much material surrounds the pair to vary, which will allow even more realistic simulations.