Why do rotation curves of galaxies imply that dark matter exists?
A) The velocity of stars rises dramatically at large distances from the centers of galaxies, implying large amounts of dark matter cause these stars to move much faster than stars at smaller distances.
B) The velocity of stars stays approximately constant at distances well beyond the visible edges of galaxies, implying that galaxies contain much more matter than what we observe in stars and gas.
C) The velocity of stars is low in the inner regions of galaxies, suggesting that dark matter is impeding their motion.
D) The velocity of stars rises quickly in the inner regions of galaxies, suggesting that unseen matter is gravitationally moving this material at faster rates than expected.
E) The velocity of stars falls slowly in the outer regions of galaxies, showing that while there is a lot of dark matter it is distributed the same way as is the visible light.

Question

Quizplus · Accepted Answer

The fact that the velocity of stars stays approximately constant at large distances from the centers of galaxies implies that there is much more matter in the galaxy than what we can observe in stars and gas. This "missing matter" is believed to be dark matter.

Why Do Rotation Curves of Galaxies Imply That Dark Matter