Stellar Mass Black
Hole, Record Breaking Wind Moving About 20 Million MPH
By Shane Nolan
February 22, 2012 - Astronomers using NASA's Chandra
X-ray Observatory have clocked the fastest wind yet
discovered blowing off a disk around a stellar-mass
black hole. This result has important implications for
understanding how this type of black hole behaves.
The record-breaking wind is moving about 20 million mph,
or about 3 percent of the speed of light. This is nearly
10 times faster than had ever been seen from a
stellar-mass black hole.
Stellar-mass black holes are born when extremely massive
stars collapse. They typically weigh between five and 10
times the mass of the sun. The stellar-mass black hole
powering this super wind is known as IGR J17091-3624, or
IGR J17091 for short.
like the cosmic equivalent of winds from a category five
hurricane," said Ashley King from the University of Michigan,
lead author of the study published in the Feb. 20 issue of The
Astrophysical Journal Letters. "We weren't expecting to see such
powerful winds from a black hole like this."
speed in IGR J17091 matches some of the fastest winds generated
by supermassive black holes, objects millions or billions of
times more massive.
surprise this small black hole is able to muster the wind speeds
we typically only see in the giant black holes," said co-author
Jon M. Miller, also from the University of Michigan. "In other
words, this black hole is performing well above its weight
unanticipated finding is that the wind, which comes from a disk
of gas surrounding the black hole, may be carrying away more
material than the black hole is capturing. "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.
Unlike winds from hurricanes on Earth, the wind from IGR J17091 is blowing in many different directions. This pattern also distinguishes it from a jet, where material flows in highly focused beams perpendicular to the disk, often at nearly the speed of light.
observations made with the National Radio Astronomy Observatory's
Expanded Very Large Array showed a radio jet from the black hole was not
present when the ultra-fast wind was seen, although a radio jet is seen
at other times. This agrees with observations of other stellar-mass
black holes, providing further evidence the production of winds can
The high speed for
the wind was estimated from a spectrum made by Chandra in 2011. Ions
emit and absorb distinct features in spectra, which allow scientists to
monitor them and their behavior. A Chandra spectrum of iron ions made
two months earlier showed no evidence of the high-speed wind, meaning
the wind likely turns on and off over time.
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. IGR J17091 is a binary system in which a sun-like star orbits the black hole. It is found in the bulge of the Milky Way galaxy, about 28,000 light years away from Earth.
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