The Milky Way galaxy is part of a group of galaxies, including several small “dwarf galaxies,” that interact with one another. The outer portion of the Milky Way, called its “halo,” is filled with clouds of gas, star clusters, dark matter and streams of stars gathered from those dwarf galaxies by the power of the Milky Way’s gravity. The Sloan Digital Sky Survey (SDSS) revealed these multiple, previously unknown streams.