One difficulty with the density wave theory is that
A) the theory fails to explain why a given spiral pattern lasts only a small fraction of the lifetime of a galaxy.
B) the theory fails to provide a mechanism for star formation.
C) astronomers are unsure of the mechanism that produces the energy output necessary to sustain the density wave.
D) the theory fails to explain the distribution of Population I and Population II stars in the galaxy.

Question

Quizplus · Accepted Answer

The density wave theory posits that the spiral arms of galaxies are areas of higher density, moving through the galaxy and triggering star formation as they go. One challenge with this theory is understanding the source of energy that maintains these density waves over long periods, as indicated in choice C.

One Difficulty with the Density Wave Theory Is That