What type of object has been proposed to explain the tremendous activity detected at the center of the Milky Way Galaxy?

Question

Quizplus · Accepted Answer

The tremendous activity detected at the center of the Milky Way Galaxy is most commonly attributed to the presence of a supermassive black hole, known as Sagittarius A*. This explanation is supported by observations of stars orbiting an invisible, extremely massive object at the galaxy's center.

What Type of Object Has Been Proposed to Explain the Tremendous