Cygnus X-1 is a binary system with one component not visible. What must the unseen component mass be for astronomers to be confident that this system contains a black hole?

Question

Quizplus · Accepted Answer

For astronomers to be confident that a binary system contains a black hole, the unseen component must have a mass more than 3 solar masses. This is because the theoretical maximum mass for a neutron star (another possible compact object) is around 2 to 3 solar masses, beyond which it would collapse into a black hole.

Cygnus X-1 Is a Binary System with One Component Not