New research from the Chandra and XMM-Newton spacecraft show that Cygnus X-1 is spinning much slower than other black holes.

Since its discovery in 1964, and its confirmation as a black hole in 1970, Cygnus X-1 has become the most intensively studied cosmic X-ray sources, with more than a thousand scientific papers published discussing its nature and origin.

The Cygnus X-1 system contains a black hole with a mass around 10 times the mass of our Sun locked in a gravitational embrace with a 20 solar mass blue supergiant star separated by just 0.2 astronomical units. Gas streams away from the star in a fast stellar wind, which is spun into a disc around the black hole. The signature X-ray emission comes from the billion degree gas as it spirals into the jaws of the black hole.

Recent observations with NASA's Chandra and ESA's XMM-Newton spacecraft have lent themselves to the study of the black hole's fuel, the stellar wind, offering scientists an insight into the rate at which the system is spinning. These latest results show that Cygnus X-1 is spinning surprisingly slowly, a finding that suggests that the black hole could have been born in an unusual type of supernova that prevented the newborn monster from acquiring as much spin as other stellar black holes.