BAADE, Wilhelm Heinrich Walter (1893-1960), German-born U.S. astronomer, educated at the University of Göttingen, whose studies of stars in the ANDROMEDA (q.v.) galaxy led him, in the 1950's,
to double the common estimate of the size and age of the universe. Begun at Mount Wilson Observatory in 1931, these studies established two major types of stars: the younger, hotter, Population I type and the older,
cooler, Population II ( see MILKY WAY). In his career in Germany prior to 1931, Baade discovered the asteroids Icarus and Hidalgo.