According to the density-wave theory, spiral arms are blue because they
A) contain many reflection nebulae from sites of young star formation.
B) contain only young stars, whose formation was triggered by the explosion of older red stars just in front of the spiral arm.
C) contain a lot of young stars formed from clouds compressed by the density wave.
D) have too much metal content to form red stars.

Question

Quizplus · Accepted Answer

The density-wave theory suggests that spiral arms are regions of higher density that compress gas clouds, leading to the formation of new, young stars, which are typically blue and hot.

According to the Density-Wave Theory, Spiral Arms Are Blue Because