The X-ray spectrum (see inset) of a binary star system consisting of a black hole and a normal star indicates that turbulent winds of multimillion degree gas are swirling around the black hole. As the illustration shows, much of the hot gas is spiraling inward toward the black hole, but about 30 percent is blowing away.
The temperature and intensity of the winds imply that powerful magnetic fields must be present. These magnetic fields, likely carried by the gas flowing from the companion star, create magnetic turbulence that generates friction in the gaseous disk and drive winds from the disk that carry momentum outward as the gas falls inward. Magnetic friction also heats the gas in the inner part of the disk to X-ray emitting temperatures.
Illustration: NASA/CXC/M.Weiss; X-ray Spectrum: NASA/CXC/ U.Michigan/J.Miller et al.
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