Black holes can orbit around each other, occasionally colliding and merging, in the most energetic events in the known Universe. However, the equations governing such mergers have remained, largely, a mystery to astronomers seeking to uncover details of the process.
University of Texas at Dallas (UT-Dallas) astronomers studied the process of pairs of rotating black holes merging into single bodies. Astrophysicists have spent decades trying to determine details of what happens to the enigmatic bodies during such collisions.
Gravity waves, warps in spacetime similar to ripples on a pond, were first predicted by Albert Einstein in his General Theory of Relativity. The famous physicist stated that supermassive bodies in binary systems would slowly spiral in toward each other as energy was lost to space through these waves. However, these waves are extremely difficult to detect, and have never been directly observed by astronomers.
"In a binary black hole system, where you have two massive objects orbiting each other and exerting forces on each other, they are accelerating and emitting gravitational waves. The energy lost to gravitational waves causes the black holes to spiral closer and closer together until they merge," Michael Kesden, assistant professor of physics at UT Dallas, said.
As rotating black holes orbit each other, each body can be described by their spin angular momentum, a measurement of the rotational rate and direction of its axis. In the case of a spinning top, the axis would point straight up-and-down when spinning first begins. Over time, the axis begins to rotate, in a process known as precession. Rotating bodies also have an orbital angular momentum, also derived from spin rate and direction.
"In these systems, you have three angular momenta, all changing direction with respect to the plane of the orbit - the two spin angular momenta and the one orbital angular momentum. The solutions that we now have describe the orientations of the precessing black hole spins," Kesden said.
The new equations will allow astrophysicists to model these systems far more efficiently than before, allowing simulations to take place in seconds, rather than years.
Astronomers observe the Universe over several wavelengths of light, using instruments designed to detect various frequencies of electromagnetic radiation. If engineers and other researchers are, one day, able to reliably detect and record gravitational waves, the instruments could herald a new age in astronomy, as important as the development of radio telescopes. Such observations could help astronomers better understand how black holes formed when the Universe was just a few percent of its current age. Such information could help researchers understand how our Universe developed into the form we see it today.
The Laser Interferometer Gravitational-Wave Observatory (Ligo) could become the first instrument to detect gravity waves, possibly by the end of 2015.
Analysis of how black holes in binary systems merge into single bodies was profiled in the journal Physical Review Letters.