An international team, including researchers from National Astronomical Observatories of China, recently found that the stellar-mass black hole in the Cygnus X-1binary system has a mass 21 times the mass of the Sun and rotates at a speed close to the speed of light.
Astronomers at the National Astronomical Observatories (NAOC) of the Chinese Academy of Sciences cooperated with researchers from the United States and Australia and reported the discovery in three papers published in the Science and The Astrophysical Journal...