Astronomers think the Milky Way has spiral arms because
A) they can see them unwinding along the celestial equator.
B) X-ray maps show that dust clouds are distributed in the disk with a spiral pattern.
C) young star clusters, HII regions, and associations outline spiral arms.
D) globular clusters outline spiral arms.
E) All of these choices are correct.

Question

Quizplus · Accepted Answer

Young star clusters, HII regions, and associations are typically found in spiral arms, providing evidence for their existence.

Astronomers Think the Milky Way Has Spiral Arms Because