A spin on black hole

The Rossi X Ray Timing Explorer has observed the first direct evidence of the rotation of a black hole. Observations show a black hole eating up a nearby companion star. The matter form the star collects on an accretion disk that is orbiting the black hole before it plunges into the black hole itself. The disk is hot enough to emit X- rays. By measuring the changes in the X-rays the scientists at the Goddard Space Flight Center, USA, have inferred that the black hole is spinning and the accretion disk is at a distance of about 45-50 kilometres from the black hole (xxx.lanl.gov/astroph, No 0104487).