It Was Recently Discovered That the Galactic Halo Contains an Outer

It was recently discovered that the galactic halo contains an outer layer.How does this outer layer compare to the inner layer?

A) The two layers are virtually identical except for their distance from the galactic nucleus.
B) The stars of the outer layer are much younger than those of the inner layer.
C) The stars of the outer layer are relatively metal-rich.
D) The stars of the outer layer orbit in the opposite sense from those of the inner layer.