Lifeboat Foundation

Distance, Mass, and Advanced Observations

To refine the measurements of Cygnus X-1, astronomers used parallax—a technique that calculates stellar distances based on their apparent motion against the backdrop of distant stars as Earth orbits the Sun. Using the Very Long Baseline Array (VLBA), a network of 10 radio telescopes across the United States, researchers tracked the system’s full orbit over six days. They determined that the black hole lies about 7,200 light-years from Earth, significantly farther than the previous estimate of 6,000 light-years.

This updated distance means its blue supergiant companion star is also more massive and brighter than expected, with a mass 40 times that of the Sun. Combined with the black hole’s orbital period, these findings provided the recalculated mass of Cygnus X-1’s black hole.