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FROM galaxies to stars to planets, almost everything in the Universe spins.
By watching X-rays from matter swirling into a black hole, an astrophysicist in
the US has shown for the first time that these rifts in the fabric of space-time
also like to have a twirl.

Tod Strohmayer of NASA鈥檚 Goddard Space Flight Center in Greenbelt, Maryland,
used the Rossi X-ray Timing Explorer satellite to sample the radiation coming
from a black hole roughly 10,000 light years from Earth and seven times the mass
of the Sun. He noticed that the X-rays waxed and waned about 450 times per
second.

Strohmayer believes the oscillating radiation comes from blobs of hot matter
travelling in the smallest stable orbit around the black hole. But, as he told
the American Physical Society meeting in Washington DC last week, the
oscillation is so fast the object must be in an orbit smaller than Einstein鈥檚
theory of gravity allows if the black hole is not rotating. A spinning black
hole, on the other hand, distorts space in a way that allows for closer orbits
and more rapidly oscillating X-rays.

There is no way around the speed limit for a non-rotating black hole, says
Virginia Trimble, an astrophysicist at the University of Maryland in College
Park and the University of California, Irvine. 鈥淚t is virtually certain that the
result is qualitatively correct,鈥� she says.

Strohmayer鈥檚 observation may help astrophysicists trying to understand
gamma-ray bursts鈥攇argantuan explosions that appear roughly once a day
somewhere in the sky. Some theorists think the bursts occur when very big stars
collapse to form black holes, but the spin of the star is crucial to whether it
emits a burst. Too much spin and it just fizzles. Too little and the black hole
swallows all the energy needed to produce the gamma rays. So it may be possible
to test this theory, Strohmayer says, by measuring the spins of many black
holes.