Walter Baade

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Walter Baade
Born (1893-03-24)March 24, 1893
Schröttinghausen, German Empire
Died June 25, 1960(1960-06-25) (aged 67)
Göttingen, West Germany
Citizenship German
Nationality German
Fields Astronomy
Institutions Hamburg-Bergedorf Observatory, Mt. Wilson, Palomar Observatory
Alma mater University of Göttingen
Doctoral students Halton Arp
Allan Sandage
Notable awards Bruce Medal 1955

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


He took advantage of wartime blackout conditions during World War II, which reduced light pollution at Mount Wilson Observatory, to resolve stars in the center of the Andromeda galaxy for the first time, which 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 Hubble in 1929.[1][2][3] He announced this finding to considerable astonishment at the 1952 meeting of the International Astronomical Union in Rome.

Together with Fritz Zwicky, he identified supernovae as a new category of astronomical objects.[4][5] Zwicky and he also proposed the existence of neutron stars, and proposed that supernovae could create neutron stars.

Beginning in 1952 he and Rudolph Minkowski identified the optical counterparts of various radio sources,[6] including Cygnus A. He discovered 10 asteroids, including notably 944 Hidalgo (long orbital period) and the Apollo-class asteroid 1566 Icarus (the perihelion of which is closer than that of Mercury) and the Amor asteroid 1036 Ganymed.


Asteroids discovered: 10
930 Westphalia March 10, 1920
934 Thüringia August 15, 1920
944 Hidalgo October 31, 1920
966 Muschi November 9, 1921
967 Helionape November 9, 1921
1036 Ganymed October 23, 1924
1103 Sequoia November 9, 1928
1566 Icarus June 27, 1949
5656 Oldfield October 8, 1920
7448 Pöllath January 14, 1948


Named after him

See also[edit]


  1. ^ Baade W (1944) The resolution of Messier 32, NGC 205, and the central region of the Andromeda nebula. ApJ 100 137-146
  2. ^ Baade W (1956) The period-luminosity relation of the Cepheids. PASP 68 5-16
  3. ^ Allen, Nick. "Section 2: The Great Debate and the Great Mistake: Shapley, Hubble, Baade". The Cepheid Distance Scale: A History. Retrieved 19 November 2011. 
  4. ^ W. Baade, F. Zwicky, 1934, "On Super-Novae". Proceedings of the National Academy of Sciences of the United States of America, 254-259.
  5. ^ Donald E. Osterbrock, Walter Baade – A Life in Astrophysics, Princeton und Oxford: Princeton University Press 2001. ISBN 0-691-04936-X. In his biography Osterbrock states, p. 32, that Baade in his inaugural lecture 1929 in Hamburg already used the German phrase "Hauptnova", "chief nova, Baades early word for a supernova" (Osterbrock).
  6. ^ 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

Further reading[edit]

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