Galactic disks appear blue because:
A)they contain no G, K, or M dwarfs.
B)they contain only blue reflection nebulae.
C)dust obscures the longer, red wavelengths.
D)O and B blue giants are much brighter than G, K, or M dwarfs.
E)dark matter gravitationally shifts all wavelengths towards the blue.

Question

Quizplus · Accepted Answer

O and B blue giants are much brighter than G, K, or M dwarfs, which makes the galactic disks appear blue. These massive stars emit most of their energy in the blue part of the spectrum and outshine the more numerous but less luminous cooler stars.

Galactic Disks Appear Blue Because