Which of the following provides the best evidence that the Milky Way's halo formed before its disk?

Question

Quizplus · Accepted Answer

The prevalence of Population II stars in the halo provides evidence that the halo formed before the disk. Population II stars are old, metal-poor stars and since they are found mostly in the halo, it suggests that the halo existed before the disk, which has more metal-rich, younger stars. The lack of gas and dust in the disk and the spiral structure in the disk do not necessarily provide evidence for when the halo and disk formed.

Which of the Following Provides the Best Evidence That the Milky