February 21, 2012
Astronomers Clock Record Wind In Stellar-Mass Black Hole
Astronomers have clocked the fastest wind yet ever discovered blowing off a disk around a stellar-mass black hole.
The team used NASA's Chandra X-ray Observatory to discover that the wind at this black hole is moving about 20 million miles per hour, or about 3 percent of the speed of light.According to NASA, this is nearly 10 times faster than other winds that have been seen around other stellar-mass black holes.
"This is like the cosmic equivalent of winds from a category five hurricane," Ashley King from the University of Michigan and lead author of the study, said in a press release. "We weren't expecting to see such powerful winds from a black hole like this."
The wind speed in the black hole matches some of the fastest winds generated by supermassive black holes, objects that are millions or billions of times more massive.
"It's a surprise this small black hole is able to muster the wind speeds we typically only see in the giant black holes," co-author Jon M. Miller, also from the University of Michigan, said. "In other words, this black hole is performing well above its weight class."
They also found that the wind may be carrying away more material than the black hole is able to capture.
"Contrary to the popular perception of black holes pulling in all of the material that gets close, we estimate up to 95 percent of the matter in the disk around IGR J17091 is expelled by the wind," King said.
Astronomers believe that magnetic fields in the disks of black holes are responsible for producing both winds and jets.
The geometry of the magnetic fields and rate at which material falls towards the black hole must influence whether jets or winds are produced.
The windy stellar-mass black hole is a binary system in which a sun-like star orbits it. It is found in the bulge of the Milky Way galaxy, about 28,000 light years away from the Earth.
The team published their findings in the Feb. 20 issue of The Astrophysical Journal Letters.
Image Caption: Artist impression of binary system containing stellar-mass black hole IGR J17091. (NASA/CXC/M.Weiss)
On the Net: