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Walter Baade

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Walter Baade
Born(1893-03-24)March 24, 1893
DiedJune 25, 1960(1960-06-25) (aged 67)
Alma materUniversity of Göttingen
Known forCoined the term "supernova" and "neutron star" with Fritz Zwicky
AwardsBruce Medal 1955
Scientific career
InstitutionsHamburg-Bergedorf Observatory, Mt. Wilson, Palomar Observatory
Doctoral studentsHalton Arp
Allan Sandage

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

Early life and education[edit]

Baade was born the son of a teacher in North Rhine-Westphalia, Germany. He finished school in 1912. He then studied maths, physics and astronomy at the universities of Münster and Göttingen. He received his PhD in 1919.[1]


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

From 1931 to 1958, he worked at Mount Wilson Observatory[2]

In 1937, the University of Hamburg wanted Baade as successor of Richard Schorr for the Hamburg Observatory, but he refused.[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. 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.[4][5][6] 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.[7][8] Zwicky and he also proposed the existence of neutron stars, and suggested supernovae might create them.[9]

Beginning in 1952, he and Rudolph Minkowski identified the optical counterparts of various radio sources,[10] including Cygnus A. He discovered 10 asteroids, 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-class 1566 Icarus, the perihelion of which is closer than that of Mercury; and the Amor-type 1036 Ganymed.

Personal life[edit]

He died in 1960 in Göttingen, West Germany.


Asteroids discovered: 10 [11]
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. ^ a b Osterbrock, D. E. (Sep 2002). "Walter Baade, Dynamical Astronomer at Goettingen, Hamburg, Mount Wilson, and Palomar Observatories". AAS/Division of Dynamical Astronomy Meeting #33. 33. Harvard Univ: 10.03. Bibcode:2002DDA....33.1003O.
  2. ^ "1955 Brude Medalist". Sonoma State University. Retrieved 4 March 2016.
  3. ^ Hentschel, Klaus; Renneberg, Monika (1995). "Eine akademische Karriere. Der Astronom Otto Heckmann im Dritten Reich" (PDF). Vierteljahrshefte für Zeitgeschichte. 43 (4): 581–610. Bibcode:1995VifZe..43..581H.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  4. ^ Baade W (1944) The resolution of Messier 32, NGC 205, and the central region of the Andromeda nebula. ApJ 100 137-146
  5. ^ Baade W (1956) The period-luminosity relation of the Cepheids. PASP 68 5-16
  6. ^ Allen, Nick. "Section 2: The Great Debate and the Great Mistake: Shapley, Hubble, Baade". The Cepheid Distance Scale: A History. Archived from the original on December 10, 2007.
  7. ^ W. Baade, F. Zwicky, 1934, "On Super-Novae". Proceedings of the National Academy of Sciences of the United States of America, 254-259.
  8. ^ Donald E. Osterbrock, Walter Baade – A Life in Astrophysics, Princeton und Oxford: Princeton University Press 2001. ISBN 0-691-04936-X.
  9. ^ Osterbrock, D. E. (2001). "Who Really Coined the Word Supernova? Who First Predicted Neutron Stars?". Bulletin of the American Astronomical Society. 33: 1330. Bibcode:2001AAS...199.1501O.
  10. ^ 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
  11. ^ "Minor Planet Discoverers (by number)". Minor Planet Center. 4 September 2016. Retrieved 7 September 2016.
  12. ^ "Walter H.W. Baade (1893 - 1960)". Royal Netherlands Academy of Arts and Sciences. Retrieved 26 January 2016.
  13. ^ "APS Member History". search.amphilsoc.org. Retrieved 2023-02-06.

Further reading[edit]

External links[edit]