Walter Baade

German-American astronomer outstanding in the use of the large telescope, who discovered ten asteroids. Baade worked at Hamburg Observatory at Bergedorf from 1919 to 1931, where in 1920 he discovered 944 Hidalgo, the first of a class of minor planets now called Centaurs which cross the orbits of the giant planets. Baade had a permanent post in the Mt. Wilson Observatory from 1931 until his retirement in 1958. He discovered the asteroid Icarus while there on 27 June 1949.

He studied the Andromeda Galaxy and recalculated the size of the known universe, doubling the previous calculation made by Hubble in 1929. He announced this finding in 1952.

Together with Fritz Zwicky, he identified supernovae as a new category of astronomical objects. Zwicky and Baade also proposed the existence of neutron stars, and suggested supernovae might create them.

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

Walter Baade died on 25 June 1960, aged 67, in Gottingham, Germany.