Rotational velocity outside the visible boundary of our Galaxy is _____ than would be expected on the basis of observed stars and gas, indicating the presence of _____.
A) zero; a vacuum
B) lower; gas
C) smaller; white dwarfs
D) higher; dark matter

Question

Quizplus · Accepted Answer

The rotational velocity outside the visible boundary of our Galaxy is higher than expected based on the mass of observed stars and gas, suggesting the presence of dark matter, which exerts gravitational effects without emitting light.

Rotational Velocity Outside the Visible Boundary of Our Galaxy Is