What evidence do we have that there is a massive black hole at the center of the Milky Way?

Question

Quizplus · Accepted Answer

The presence of rapidly rotating gas very close to the center of the Milky Way is evidence for the existence of a massive black hole. This gas is being pulled in by the gravitational force of the black hole, causing it to rotate rapidly around the center. This phenomenon is known as the "central black hole hypothesis."

Answer: D
 The density of stars increases as distance from the center decreases, which is consistent with the presence of a massive black hole. With more mass at the center, the gravitational pull is stronger, making it easier for stars to be held in orbit around the black hole. This creates a higher concentration of stars near the center, as compared to the outer regions of the galaxy.

What Evidence Do We Have That There Is a Massive