Milky Way's 'little cousins' may hold clues about infant universe

Ultra-faint dwarf galaxies-tiny satellite galaxies orbiting the Milky Way-have long been seen as cosmic fossils. Now, a new study published today in Monthly Notices of the Royal Astronomical Society uses an unprecedented set of simulations to show just how powerfully these faint systems can reflect the conditions of the early universe and tell us why some galaxies grew and others did not.