By Ron Cowen
A new study has identified stellar crumbs from what may be the Milky Way’s most recent meal — a dwarf galaxy devoured about 700 million years ago. The discovery provides fresh evidence for the leading theory of galaxy formation, which holds that the Milky Way and other large, modern-day galaxies began small and continue to grow by consuming or merging with their neighbors.
The stream of 15 stars discovered by Mary Williams of the Astrophysical Institute Potsdam in Germany and her colleagues all have similar speeds and chemical compositions. It’s those shared properties that set the elongated grouping of stars, located in the constellation Aquarius, apart from the 250,000 other stars across the Milky Way surveyed by the Australian Astronomical Observatory in Siding Spring, Williams and colleagues report in the Feb. 20 Astrophysical Journal.