You are studying a mystery companion to an evolved star, with mass transfer happening. Which of the following properties suggests that the companion is definitely a black hole?
A) The mystery companion has a mass of over 1.4 solar masses.
B) The mystery companion has a mass of over 3 solar masses.
C) The mystery companion has an X-ray emitting accretion disk.
D) The mystery companion gives off periodic X-ray bursts.
Question 2
Active galaxies emit most of their radiation as visible light.
Indicate whether the statement is true or false