NASA's Chandra finds fastest wind from stellar-mass black hole

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, the U.S. space agency announced Tuesday. 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 three 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. "This is 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 this week in The Astrophysical Journal Letters. "We weren't expecting to see such powerful winds from a black hole like this." The wind speed in IGR J17091 matches some of the fastest winds generated by supermassive black holes, objects 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," said coauthor Jon M. Miller, also from the University of Michigan. "In other words, this black hole is performing well above its weight class." Another 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. Astronomers believe that magnetic fields in the disks of black holes are responsible for producing the winds. The geometry of the magnetic fields and rate at which material falls towards the black hole must influence whether 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.