What is a rotation curve?
Answer
A) a precise description of the shape of a star's orbit around the center of the Milky Way Galaxy
B) a graph showing how orbital velocity depends on distance from the center for a spiral galaxyC) a curve used to decide whether a star's orbit places it in the disk or the halo of a spiral galaxy
D) a graph that shows a galaxy's mass on the vertical axis and size on the horizontal axis
