Walter Baade

 ( 1893 Births ) 

From 1931 to 1958, he worked at Mount Wilson Observatory in Los Angeles, California.

In 1937, the University of Hamburg wanted Baade as successor of Richard Schorr for the Hamburg Observatory, but he refused.

During World War II, while working at Mount Wilson Observatory, Baade took advantage of wartime blackout conditions (which reduced light pollution), to resolve stars in the center of the Andromeda Galaxy for the first time. These observations led him to define distinct "populations" for stars (Population I and Population II). The same observations led him to discover that there are two types of Cepheid variable stars. Using this discovery he recalculated the size of the known universe, doubling the previous calculation made by Edwin Hubble in 1929.Baade W (1944) The resolution of Messier 32, NGC 205, and the central region of the Andromeda nebula. ApJ 100 137-146Baade W (1956) The period-luminosity relation of the Cepheids. PASP 68 5-16 He announced this finding to considerable astonishment at the 1952 meeting of the International Astronomical Union in Rome.

Together with Fritz Zwicky, he identified as a new category of astronomical objects.W. Baade, F. Zwicky, 1934, " On Super-Novae". Proceedings of the National Academy of Sciences of the United States of America, 254-259.Donald E. Osterbrock, Walter Baade – A Life in Astrophysics, Princeton und Oxford: Princeton University Press 2001. . Zwicky and he also proposed the existence of , and suggested supernovae might create them.

Beginning in 1952, he and Rudolph Minkowski identified the optical counterparts of various radio astronomy sources,Baade, W. and Minkowski, R., 1954. Identification of the Radio Sources in Cassiopeia, Cygnus A, and Puppis A. Astrophysical Journal, Vol. 119, p. 206-214 (January 1954) ADS: 1954ApJ...119..206B including Cygnus A. He discovered 10 , including 944 Hidalgo, which has a long orbital period (it is actually the first centaur ever discovered, although they were not recognized as a distinct dynamical class until 1977); the Apollo asteroid-class 1566 Icarus, the perihelion of which is closer than that of Mercury; and the Amor asteroid-type 1036 Ganymed.

Awards

• Foreign membership of the Royal Netherlands Academy of Arts and Sciences (1953)
• Elected Member of the American Philosophical Society (1953).
• Gold Medal of the Royal Astronomical Society (1954)
• Bruce Medal (1955)
• Henry Norris Russell Lectureship of the American Astronomical Society (1958)

• Asteroid 1501 Baade
• The crater Baade on the Moon
• Vallis Baade, a vallis (valley) on the Moon
• One of the two Magellan
• The asteroid 966 Muschi, after his wife's nickname

• Baade's Window, an observational area he identified in the 1940s as being relatively free of dust that presents a view of the Galactic Center in Sagittarius
• Baade's Star, now known as the Crab Pulsar, was first identified as being directly associated with the Crab Nebula by him.
• Baade-Wesselink method, a method for determining the distance of a Cepheid variable star

• Donald E Osterbrock (2001). 069104936X, Princeton University Press. . 069104936X

• Bruce Medal page
• Awarding of Bruce Medal
• Awarding of RAS gold medal

• JRASC 55 (1961) 113
• MitAG 14 (1961) 5
• QJRAS 2 (1961) 118