What is observed to happen to the velocities of stars that reside at greater distances from the center of the galaxy?
A) They move slower and slower.
B) They move faster and faster.
C) They vary greatly in a random fashion.
D) They essentially stay the same.

Question

Quizplus · Accepted Answer

Stars at greater distances from the center of the galaxy have velocities that essentially stay the same, which is contrary to the expected decrease in velocity with distance. This observation is one of the key pieces of evidence for the existence of dark matter.

What Is Observed to Happen to the Velocities of Stars