The baryon halo of the Milky Way: A fossil record of its formation

Astronomers believe that the baryon (stellar) halo of the Milky Way retains a fossil imprint of how it was formed. But a vast Literature shows that th e struggle to interpret the observations within a consistent framework cont inues. The evidence indicates that the halo has built up through a process of accretion and merging over billions of years, which is still going on at a Low Level. Future satellite missions to derive three-dimensional space m otions and heavy element (metal) abundances for a billion stars will disent angle the existing web and elucidate how galaxies Like our own came into ex istence.