Rotation curves for spiral galaxies show
A) most have dark halos.
B) most of the mass lies in the nucleus.
C) they are slowing down.
D) rotation speed drops off further from the nucleus.
E) no relation to mass.

Question

Quizplus · Accepted Answer

Rotation curves of spiral galaxies indicate that the velocity of stars and gas in the outer parts of galaxies remains constant or even increases slightly, rather than dropping off as expected if the visible matter were all there is. This suggests the presence of a significant amount of unseen mass, referred to as dark matter, in a halo around the galaxies.

Rotation Curves for Spiral Galaxies Show