Black hole detection

An X-ray-detecting satellite found evidence suggesting the presence of a black hole, Cygnus X-1, near a massive star. It was shown that the large star and black hole were revolving around each other, and that Cygnus X-1 must be 5x as massive as sun.
 C. T. Bolt Canada 1971 Black hole detection

An X-ray-detecting satellite found evidence suggesting the presence of a black hole, Cygnus X-1, near a massive star. It was shown that the large star and black hole were revolving around each other, and that Cygnus X-1 must be 5x as massive as sun.