A theoretical model of a galaxy like the Milky Way, showing trails of stars torn from disrupted satellite galaxies that have merged with the central galaxy. The structures seen in the SDSS-II star maps support this prediction of a complicated outer Milky Way. The region shown is about one million light years on a side; the sun is just 25,000 light years from the center of the Milky Way and would appear close to the center of this picture. Credit: K. Johnston, J. Bullock