In which constellation is the X-ray binary Cygnus X-1 located? The answer is Cygnus.
Cygnus X-1 is a famous X-ray binary in the constellation Cygnus, whose name means “swan” in Latin. The system lies in the Milky Way roughly 6,000 light-years from Earth and contains a massive blue supergiant star orbiting a compact object that is a black hole.
Astronomers discovered Cygnus X-1 as an X-ray source in 1964 during a sounding-rocket flight. The black hole’s intense gravity pulls gas from its companion. As that material spirals inward, it forms a hot accretion flow and releases powerful X-rays, making the otherwise invisible system detectable.
The name itself is a useful clue: “Cygnus” identifies the region of the sky, while “X-1” indicates an X-ray source in that constellation. It is not the name of a separate constellation. Cygnus X-1 was the first object widely accepted as containing a black hole, although astronomers infer the black hole from its mass and behavior rather than seeing the black hole directly.