Scientists Found Flashes of Light from Colliding Black Holes
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Astronomers detected a potential gravitational-wave signature that may have helped them discover possible light from colliding black holes.
The name itself suggests that ‘Black Holes’ are not supposed to produce any light. Ever since the discovery of the invisible phenomenon, this is exactly what we knew until last month. According to a recent study, scientists may have detected a flash of light from colliding black holes.
On 21st May 2019, gravitational-wave detectors of the Earth caught a possible signal of the collision between two massive objects. 35 days later, the Zwicky Transient Facility (ZTF) picked up a quasar flare in the same sky region. This made the researchers wonder that they might have spotted rare light from colliding black holes. Daniel Stern, an Astrophysicist at the Jet Propulsion Laboratory of NASA, talked about this discovery in the following words:
“This detection is extremely exciting. There’s a lot we can learn about these two merging black holes and the environment they were in based on this signal that they sort of inadvertently created.”
What Might Have Happened?
The model presented by the researching team indicates that two stellar-sized black holes merged within the accretion disk of a quasar. The term ‘quasar’ refers to a bright object that is powered by a supermassive black hole.
The researchers claimed that the light from colliding black holes was actually caused by the stirring up of hot gas. This gas (alongside other materials) fills the accretion disk around every supermassive black hole. The merged black hole heated this gas as it shot out of the collision at a very high speed. Talking about the flare, Mansi Kasliwal (a Co-author of the study who is an Astronomer at Caltech) said,
“Supermassive black holes like this one have flares all the time. They are not quiet objects, but the timing, size, and location of this flare were spectacular.”
They further explained that the flare was delayed because the light was slowed down by the opaque disk. The light ultimately faded away after about 40 days as the fast-moving black hole escaped the disk. K.E. Saavik referred to the violent interaction of supermassive black holes with the surrounding objects by saying,
“These objects swarm like angry bees around the monstrous queen bee at the center. They can briefly find gravitational partners and pair up but usually lose their partners quickly to the mad dance. But in a supermassive black hole’s disk, the flowing gas converts the mosh pit of the swarm to a classical minuet, organizing the black holes so they can pair up.”
Future Prediction
If this theory is correct, the mass of the merged black hole will be around 150 solar masses. For such a large merger to happen, it is necessary to have multiple smaller mergers of black holes. Only then, we can have two black holes that are huge enough to cause such a massive collision. A quasar is for this kind of cumulative building because it is concentrated with black holes.
The researchers believe that the merged black hole is now orbiting the central supermassive black hole. According to their model, it will continue to do so for about 1.6 years before crashing back into the disk. Such an explosive clash will definitely reignite the flares. This is the reason why the researching team wants to keep an eye on this quasar for some years.
Chances of Other Possibilities
Although quasars can ordinarily vary in brightness, the researching scientists found the observed flaring to be inconsistent with past variations. Similarly, they ruled out the possibility of the light coming from a supernova. Despite that, Matthew Graham, the Project Scientist for ZTF, clarified that it’s NOT confirmed that their explanation is 100% correct. He said,
“The flare occurred on the right timescale, and in the right location, to be coincident with the gravitational-wave event. We conclude that the flare is likely the result of a black hole merger, but we cannot completely rule out other possibilities.”
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