How do we measure directly that AGNs have black holes at their centers?
A) We know that massive stars make black holes, and most galaxies contain a lot of massive stars.
B) We know black holes are made of dark matter, and galaxies are mostly made up of dark matter.
C) We know that black holes emit radio waves, and many AGNs are bright at radio waves.
D) We measure that the mass of the black hole is increasing as material falls into it.
E) In some systems, we can see both redshifted and blueshifted emission lines from material orbiting around the black hole.

Question

Quizplus · Accepted Answer

In some AGNs, the presence of both redshifted and blueshifted emission lines indicates material is orbiting a massive object, consistent with a black hole at the center.

How Do We Measure Directly That AGNs Have Black Holes