A map of the Milky Way Galaxy deduced from radio observations of the 21-cm line emission from cool hydrogen gas and observations of spiral arm tracers such as giant molecular clouds reveals
A) two spiral arms, one on each side of the Galaxy.
B) a smooth distribution of stars, characteristic of an elliptical galaxy.
C) at least four spiral arms.
D) one spiral arm that wraps around the Galaxy several times.

Question

Quizplus · Accepted Answer

The Milky Way Galaxy, as deduced from radio observations of the 21-cm line emission from cool hydrogen gas and observations of spiral arm tracers such as giant molecular clouds, reveals at least four spiral arms, not just one or two, and it does not have a smooth distribution of stars characteristic of an elliptical galaxy.

A Map of the Milky Way Galaxy Deduced from Radio