SS 433

SS 433 is a microquasar or eclipsingX-ray binarysystem, consisting of a stellar-mass black holeaccreting matter from an A-typecompanion star. SS 433 is the first discovered microquasar. It is at the centre of the supernova remnant W50.

SS 433's designation comes from the initials of two astronomers at Case Western Reserve University: Nicholas Sanduleak and Charles Bruce Stephenson. It was the 433rd entry in their 1977 catalog of stars with strong emission lines. Its emission lines were studied by Mordehai Milgrom in 1979.