NASA Observatory records 20 million-mph winds off stellar-mass black hole
February 23, 2012
NASA's Chandra X-ray Observatory has recorded ultra-fast 20 million mph (32 million km/h) winds roaring from a gas disk around the stellar-mass black hole IGR J17091-3624. The wind speeds are a record, a factor of ten greater than any previously recorded, for a black hole of this kind. It is hoped the surprise discovery will shed new light on the behavior of stellar-mass black holes.
In fact winds of this speed are generally associated with supermassive black holes millions (or even billions) of times as massive. Stellar-mass black holes have a mass of at least three, but typically between five and 10, solar masses, and are caused by the collapse of massive stars.
The speed of the winds (about three percent of the speed of light) is not the only surprise to researchers. The multi-directional winds also seem to be carrying more matter than is being captured by the black hole.
"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," said the University of Michigan's Ashley King, lead author of the study published in The Astrophysical Journal Letters earlier this week.
The winds from black hole accretion disks are believed to be magnetically driven. These forces are also thought to generate radio jets, differentiated from winds by their terrific speed (almost the speed of light) in one direction - directly perpendicular to the disk itself.
The wind speeds were recorded in 2011 based on a spectrum of iron ions recorded by Chandra. Interestingly, a similar recording made two months prior suggested no such ultra-winds, and so it is thought that they occur cyclically. Complimentary observations from the National Radio Astronomy showed that no radio jet was in evidence at the time of the high-speed winds, reinforcing the belief that the occurrence of winds can interfere with such jets.
Launched in 1999, the Chandra X-ray Observatory is the third of NASA's four Great Observatories - the Hubble Telescope, Compton Gamma Ray Observatory, and the Sptizer Telescope being the others.