Compared to stars forming in the spiral arms today, what is characteristic of the composition of very old stars born in the galactic halo?

Answer

They exhibit very low metallicity.

Stars born in the galactic halo are very old and exhibit very low metallicity, meaning their composition is closer to the original primordial mix of pure hydrogen and helium.

Compared to stars forming in the spiral arms today, what is characteristic of the composition of very old stars born in the galactic halo?
astronomyhydrogencompositionstellarstars