Question

Why are there older, Population II stars in the halo and not in the plane of the Milky Way?Pop II stars are only stars that have been stolen from other, older galaxiesVery old Pop III stars gradually evolve to appear like Pop II starsPop II stars are the left-over stars that formed before gas settled into the planePop II stars migrate from the plane to the halo over timePop II stars only form in globular clusters, which are found primarily in the halo

Answer 1

Pop II stars are the left-over stars that formed before gas settled into the plane. The halo is the oldest part of the Milky Way galaxy and contains older stars that formed when the galaxy was still in its early stages. As the Milky Way evolved and gas settled into the plane, newer generations of stars formed in the disk. Therefore, Pop II stars are found primarily in the halo and not in the plane of the Milky Way.