The end of a black hole s evolution may be a mind-bending kind of space-time
independent of time. A new study proposes a method to tell how far any black
hole is from reaching this end state.
Black holes are some of the weirdest things in the universe. They occur when
mass is packed into a tiny volume, squished to its ultimate density.
Though observations suggest black holes are prevalent in the universe,
scientists still don't really understand what goes on inside them. The
equations of general relativity usually used to understand the physics of the
universe break down in these cases.
"It is really beyond the physics we know," said Juan Antonio Valiente Kroon, a
mathematician at Queen Mary, University of London. "To understand what happens
inside a black hole, we need to invent new physics."
Mercifully, the physics for the end state of a black hole is somewhat simpler.
A solution to the equations of general relativity was found that produced a
situation called "Kerr spacetime." Scientists now think Kerr spacetime is what
happens when a black hole has reached its final evolutionary state.
"Mainly the equations of relativity are so complex that for relativistic
systems, the only way you can probe these equations is by means of computer,"
Valiente Kroon told SPACE.com. "Solutions like this Kerr solution are really
exceptional. The Kerr solution is one of the few explicitly known solutions to
general relativity that have a direct physical meaning."
Kerr spacetime is time-independent, meaning that nothing in Kerr spacetime
changes over time. In effect, time stands still. A black hole in such a state
is essentially stationary.
"One could say once it has reached this stage, there are no further processes
taking place," Valiente Kroon said.
In their new study, Valiente Kroon and Thomas Backdahl, his colleague at Queen
Mary, have calculated a formula to determine how close a black hole is to
reaching the Kerr state.
This can happen very quickly even in seconds depending on the object's
mass.
To apply the formula, scientists would examine the region around a black hole
called its event horizon. Once mass, or even light, passes within the event
horizon of a black hole, it cannot escape the black hole's gravitational
clutches.
The researchers think their development could aid scientists who are building
computer simulations of black holes and aiming to align them with observations
of actual black holes.
Astronomers think most galaxies, including our own Milky Way, host supermassive
black holes in their centers. Some researchers suspect that these are actually
Kerr black holes.
Valiente Kroon and Backdahl detail their work in the Jan. 19 issue of the
journal Proceedings of the Royal Society A.