The Milky Way galaxy possesses a distinct outer halo that orbits in the opposite direction from its inner halo and the rest of the galaxy, researchers say. This second halo contains some of the most primitive stars in the universe, offering new evidence about how the galaxy formed.
Some scientists had previously suspected that a portion of the stars in the Milky Way travel in a different direction from the rest. But data on such stars were too sparse to conclude that an entire second halo existed.