The disks of spiral galaxies appear blue because
A) they are moving toward us.
B) they contain a relatively high concentration of low-mass stars.
C) they contain active regions of star formation.
D) they contain more metals that, when ionized, emit blue light.
E) stars collide with each other frequently in these dense regions and explode as Type Ia supernovae.

Question

Quizplus · Accepted Answer

The blue color of spiral galaxy disks is due to the presence of young, hot, massive stars that form in active star-forming regions. These stars emit more blue light, giving the galaxy its blue appearance.

The Disks of Spiral Galaxies Appear Blue Because