How has the diameter of the black hole candidate Cygnus X-1 been estimated?
A) from the angular size in the sky of Cygnus X-1 and its known distance from Earth
B) from the time scale of the flickering of the X-rays Cygnus X-1 emits
C) from the orbital period around a companion star of Cygnus X-1
D) from the length of time Cygnus X-1 blocks off the light from its companion star when Cygnus X-1 passes in front of (eclipses) its companion, as seen from Earth

Question

Quizplus · Accepted Answer

The diameter of the black hole candidate Cygnus X-1 has been estimated from the time scale of the flickering of the X-rays it emits, which provides information about the size of the region where the X-rays are produced.

How Has the Diameter of the Black Hole Candidate Cygnus