The Origins Of Gravitational Wave-Inducing Black Holes

Using supercomputer-aided simulations, scientists in Japan have examined how binary black holes responsible for gravitational waves may have originated.

AsianScientist (Dec. 29, 2017) – In a study published in the journal Physical Review Letters, scientists in Japan have simulated how two black holes could be formed within a massive, collapsing star.

Far from earth, two black holes orbit around each other, propagating waves that bend time and space. The existence of such waves—gravitational waves—was first predicted by Albert Einstein over a century ago based on his theory of general relativity. However, it was not until 2015 that the Laser Interferometer Gravitational-Wave Observatory (LIGO) was able to detect gravitational waves for the first time, earning three scientists from the LIGO team the 2017 Nobel Prize in physics.

The detection of gravitational waves has resulted in a new field of gravitational wave astronomy. But as with many discoveries, for every mystery solved, new questions have arisen. For example, scientists are now wondering: how did gravitational wave-inducing black holes originate?

In the present study, Mr. Joseph Fedrow of Kyoto University’s Yukawa Institute for Theoretical Physics, in collaboration with the International Research Unit for Advanced Future Studies, has determined what gravitational waves might look like if two black holes formed inside a massive, collapsing star.

“Although gravitational waves have allowed us to directly detect black holes for the first time, we still don’t know the exact origins of these particular black holes,” Fedrow explained. “One idea is that these black holes formed during dynamical fragmentation of the inner core of a dying star undergoing gravitational collapse.”

This, according to Fedrow, could have resulted in two of the fragments becoming black holes and orbiting around each other in the remains of the stellar environment.

To test this proposal, the team used supercomputers and the tools of numerical relativity to create a model of two black holes in such surroundings. The output of their analysis was subsequently compared against LIGO’s observational data.

“Our results were measurably different,” said Fedrow. “We showed that if black holes formed in a high-density, stellar environment, then the time it takes for them to merge shortens. If the density is lowered to levels more similar to vacuum, then the resulting gravitational waves match those of the event observed.”

In addition to shedding light on the dynamics of binary black holes, these results reaffirm that the first waves detected by LIGO came from black holes in an empty region of space.

“In this exciting, new era of gravitational wave astronomy, we don’t know what we’ll find, or where it will lead us,” said Fedrow. “But our work here will help to illuminate untrodden paths and shine a light upon the darkest of objects in the universe.”

The article can be found at: Fedrow et al. (2017) Gravitational Waves from Binary Black Hole Mergers inside Stars.


Source: Kyoto University; Photo: Joseph M. Fedrow.
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