Dec 19 2017
Snapshot of gravitational waves propagating from binary black holes merging inside of a star. CREDIT Kyoto University, Joseph M. Fedrow
Two black holes orbit around each other, far from earth, in order to propagate waves that bend space and time.
The presence of such waves, known as gravitational waves, was originally predicted by Albert Einstein over a century ago based on his theory of general relativity. Einstein was indeed right as always.
However, it was not until 2015 that the Laser Interferometer Gravitational-Wave Observatory was able to identify gravitational waves for the very first time: discoveries which earned the LIGO team the Nobel Prize in physics after two years.
Besides the shockwave sent by this discovery across the scientific community, it also provided researchers the new field of gravitational wave astronomy. However, as with a number of discoveries, for every mystery that has been solved, new questions have indeed arisen.
One new puzzle relates to the question: how did those gravitational wave-inducing black holes originate?
Reporting in the journal Physical Review Letters, Joseph Fedrow of Kyoto University's Yukawa Institute for Theoretical Physics -- in association with the International Research Unit for Advanced Future Studies -- has established what gravitational waves could look like if two black holes developed 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. One idea is that these black holes formed during dynamical fragmentation of the inner core of a dying star undergoing gravitational collapse.
Joseph Fedrow, Yukawa Institute for Theoretical Physics, Kyoto University
According to Fedrow, this could have resulted in two of the fragments transforming into black holes and then orbiting around each other within the remains of the stellar environment.
In order to test this proposal, the team employed supercomputers and the tools of numerical relativity to develop a model of two black holes in such surroundings. The output was compared against LIGO's observational data after many long hours of computation.
Our results were measurably different. Showing 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.
Joseph Fedrow, Yukawa Institute for Theoretical Physics, Kyoto University
Besides shedding light on the dynamics of binary black holes, these results further reaffirm that the first waves discovered by LIGO were generated 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. But our work here will help to illuminate untrodden paths, and shine a light upon the darkest of objects in the universe.
Joseph Fedrow, Yukawa Institute for Theoretical Physics, Kyoto University