Wilhelm Heinrich Walter Baade (March 24, 1893 – June 25, 1960) was a German astronomer who worked in the United States from 1931 to 1959.

[3] At Mount Wilson Observatory, during World War II, he took advantage of wartime blackout conditions (which reduced light pollution), to resolve stars in the center of the Andromeda Galaxy for the first time.

Using this discovery he recalculated the size of the known universe, doubling the previous calculation made by Edwin Hubble in 1929.

[4][5][6] He announced this finding to considerable astonishment at the 1952 meeting of the International Astronomical Union in Rome.

[9] Beginning in 1952, he and Rudolph Minkowski identified the optical counterparts of various radio sources,[10] including Cygnus A.