Although it hasn't been observed (yet), why do astronomers think that the Milky Way is embedded in a halo of dark matter?
A) Theory predicts that there should be more black holes than we've so far detected.
B) Stars in the outer regions of the Galaxy are orbiting faster than expected.
C) Due to its large size, the light from stars on the other side of the Milky Way has not reached us yet.
D) Astronomers have detected neutrinos from unseen sources.

Question

Quizplus · Accepted Answer

Stars in the outer regions of the Galaxy are orbiting faster than expected, which suggests the presence of additional unseen mass, attributed to dark matter, providing the necessary gravitational pull.

Although It Hasn't Been Observed (Yet), Why Do Astronomers Think