MIT: Spinning black hole leaves dent in space-time
Courtesy Massachusetts Institute of Technology
and World Science staff
Scientists say they have found a black hole that has chiseled a dent in the fabric of space and time, like a dimple in one’s favorite spot on the sofa.
They say the finding may help scientists measure a black hole’s weight and how it spins—two long-sought measurements—based on the extent of this indentation.
Using a NASA satellite, the team found identical patterns in the X-ray light emitted near the black hole nine years apart.
Black hole regions are notoriously chaotic, generating light that has a range of different energies. Similarities in light seen nine years apart imply something very fundamental is producing the stable pattern, the researchers said.
That would be the warping of space and time, which Einstein predicted black holes would cause.
Jeroen Homan of the Massachusetts Institute of Technology and colleagues planned to present the finding this week at the annual meeting of the American Astronomical Society in Washington, D.C.
Black holes form when a very massive star runs out of fuel. Without the power to stay puffed up, the star implodes and the core crushes itself through its own gravity to a point of infinite density. Its fierce gravitational pull
then sucks in everything that comes nearby, including light.
Einstein’s theory of relativity holds
that the overpowering gravity of black holes would also warp this fabric
of space and time. Clocks near a black hole would slow down. Objects in
the vicinity would stretch out like spaghetti as they plummet to their
Black holes have a theoretical border called an event horizon, the point of no return where anything that passes can never escape.
Homan’s team said they observed a region less than 100 miles from the event horizon of a black hole system called GRO J1655-40.
Here, an object can orbit a black hole fairly
peacefully, they said. But occasionally it wobbles in precise patterns.
This would be a direct result of how the black hole deforms space and
time, which in Einstein’s theory is a unified concept called spacetime.
Using the satellite, called the Rossi X-ray Timing Explorer, the
researchers watched the system about twice a day for eight months. Gas from a companion star was falling toward the black
hole, they said. It was giving off X-ray light as a result of
dramatically heating up as it fell.
The team found fluctuations in the X-ray light, called quasi-periodic oscillations, thought to come from wobbling blobs of gas whipping around the black hole. The vibrations had measured speeds of 300 and 450 Hertz (vibrations per second)—the same as a pair of oscillations observed in 1996.
“The fact that we found the exact same frequency of X-ray oscillations nine years later is likely no coincidence,” said Homan. “The black hole is still singing the same tune. The oscillations are created by a groove hammered into space-time by the black hole. This phenomenon has been suspected for a while, but now we have strong evidence to support it.”
Previous observations have determined that the black hole weighs about 6.5 times as much as than the sun, Miller said.
The vibrations “are determined by the mass of the black hole and also by how fast it spins,” he added. “Those measurements—mass and spin—have been difficult to obtain. Fortunately, we already have an estimate of the mass of this black hole. By understanding the behavior of matter so close to the black hole’s edge, we can now begin to determine the spin and thus, for the first time, completely describe the black hole.”
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