If you tried to stay still in its vicinity, you couldn't; you'd be dragged around at high speed as if you were riding on a giant flywheel.

In reality, gas falling into the black hole is whirled in that way. It radiates energy, in the form of X-rays, more intensely than it would do if space were still by tapping into the black hole's internal energy stream.

The European Space Agency (ESA)'s big X-ray detecting satellite, XMM-Newton, was specifically designed to detect this form of energy.

With this finding, it has chalked up another notable success in its investigations of the black holes -- mysterious regions of space where gravity is so strong that light can't escape.

High speeds and intense gravity affect the energy of X-rays emitted from iron atoms very close to a black hole. By detecting the resulting spread of energies with XMM-Newton, astronomers can diagnose the conditions there.

The weird effect of a spinning black hole on its surroundings is linked to Albert Einstein's theory of gravity, in which the fabric of space itself becomes fluid.

XMM-Newton first discovered such black-hole flywheels in galaxies many millions of light-years away. Now, in findings to be formally reported next month, it sees the same thing much closer to home in our own Galaxy, the Milky Way.

A US-European team of astronomers made the discovery last September during an outburst from the vicinity of a black-hole candidate called XTE J1650-500. This object is about 10 times heavier than the Sun.

A similar black-hole flywheel in another galaxy, already examined by XMM-Newton, is a million times more massive than that, and 4,000 times more distant.

"Now we've seen this astonishing behavior across a great range of distances and masses," comments Matthias Ehle, a member of the team at ESA's Villafranca satellite station in Spain. "Our hopes that XMM-Newton would vastly improve our understanding of black holes have not been disappointed."

The astronomers describe their observations and their interpretations in a paper to be published in Astrophysical Journal Letters on May 10, 2002. The lead author is Jon Miller of the Massachusetts Institute of Technology.

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European Space Agency

29-Apr-2002