Question

There are stars located in the center bulge of the Milky Way and the spiral arms of the Milky Way. What is the difference between the stars at the center bulge and the stars in the arms?
A. The stars at the center bulge are typically smaller than the stars in the arms.
B. The stars at the center bulge are typically older than the stars in the arms.
C. The stars at the center bulge are typically colder than the stars in the arms.
D. The stars at the center bulge are typically brighter than the stars in the arms.

Answer 1

B. The stars in the central bulge are typically older.

Explanation: the bulge is dominated by older, redder (Population II-like) stars and relatively little recent star formation, while the spiral arms contain lots of gas and dust and active star formation, so they host many younger, hotter, massive (blue) stars.