The Milky Way feasted on a smaller galaxy 10 billion years ago
The doomed galaxy’s stars still roam the sky, moving in the opposite direction of other stars
GOBBLE GOBBLE The young Milky Way, shown in an artist’s impression, swallowed a smaller galaxy about 10 billion years ago. The smaller galaxy’s stars are shown with yellow arrows depicting their direction of motion.
ESA (artist’s impression and composition); H.H. Koppelman, A. Villalobos and A. Helmi (simulation); Hubble/ESA/NASA (galaxy image), CC BY-SA 3.0 IGO