'Death spiral' around Cygnus XR-1

The Hubble telescope may have, for the first time, provided direct evidence for the existence of black holes by observing how matter disappears when it falls beyond the 'event horizon', the boundary between a black hole and the outside universe. Astronomers found their evidence by watching the fading and disappearance of pulses of ultraviolet light from clumps of hot gas swirling around a massive, compact object called Cygnus XR-1. This activity suggests that the hot gas fell into a black hole.