APOD: Black Hole Candidate Cygnus X-1

apod.nasa.gov — Is that a black hole? Quite possibly. The Cygnus X-1 binary star system contains one of the best candidates for a black hole. The system was discovered because it is one of the brightest X-ray sources on the sky, shining so bright it was detected by the earliest rockets carrying cameras capable of seeing the previously unknown X-ray sky. Aug 11, 2008 View in Crawl 4