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

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



After receiving his PhD in 1919, Baade worked at Hamburg Observatory at Bergedorf from 1919 to 1931.[1] There in 1920 he discovered 944 Hidalgo, the first of a class of minor planets now called Centaurs which cross the orbits of giant planets.

He worked at Mount Wilson Observatory from 1931 to 1958.[2] There, 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. 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 Hubble in 1929.[3][4][5] 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.[6][7] 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,[8] including Cygnus A. He discovered 10 asteroids, including 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 [9]
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 alsoEdit


  1. ^ Osterbrock, D. E. (Sep 2002). "Walter Baade, Dynamical Astronomer at Goettingen, Hamburg, Mount Wilson, and Palomar Observatories". SAO/NASA ADS Astronomy Abstract Service. Harvard Univ. Retrieved 4 March 2016. 
  2. ^ "1955 Brude Medalist". Sonoma State University. Retrieved 4 March 2016. 
  3. ^ Baade W (1944) The resolution of Messier 32, NGC 205, and the central region of the Andromeda nebula. ApJ 100 137-146
  4. ^ Baade W (1956) The period-luminosity relation of the Cepheids. PASP 68 5-16
  5. ^ Allen, Nick. "Section 2: The Great Debate and the Great Mistake: Shapley, Hubble, Baade". The Cepheid Distance Scale: A History. Retrieved 19 November 2011. 
  6. ^ W. Baade, F. Zwicky, 1934, "On Super-Novae". Proceedings of the National Academy of Sciences of the United States of America, 254-259.
  7. ^ 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).
  8. ^ 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
  9. ^ "Minor Planet Discoverers (by number)". Minor Planet Center. 4 September 2016. Retrieved 7 September 2016. 
  10. ^ "Walter H.W. Baade (1893 - 1960)". Royal Netherlands Academy of Arts and Sciences. Retrieved 26 January 2016. 

Further readingEdit

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