What evidence suggests that the protogalactic cloud that formed the Milky Way resulted from several collisions among smaller clouds?
A)The Milky Way is the central galaxy of a dense cluster of galaxies.
B)Halo stars differ in age and heavy- element content, but these variations do not seem to depend on the stars' distance from the galactic center.
C)The stars in the halo of the Milky Way are organized into several dense clusters arranged throughout the halo.
D)The Milky Way resembles an elliptical galaxy more than other spirals do.
E)The bulge of the Milky Way is surrounded by many globular clusters, just as elliptical galaxies are.

Question

Quizplus · Accepted Answer

Halo stars differing in age and heavy-element content suggest that the protogalactic cloud that formed the Milky Way resulted from several collisions among smaller clouds. If the Milky Way had formed from a single cloud collapsing, all halo stars would have formed at the same time and with the same heavy-element content. However, since different parts of the protogalactic cloud would have had different compositions, the different ages and heavy-element contents of halo stars can be explained by multiple collisions among smaller clouds.

What Evidence Suggests That the Protogalactic Cloud That Formed the Milky