Walter Baade

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

Biography

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. This discovery led him to recalculate 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 (whose perihelion is closer than that of Mercury) and the Amor asteroid 1036 Ganymed.

Honors

Awards

• Gold Medal of the Royal Astronomical Society (1954)
• Bruce Medal (1955)
• Henry Norris Russell Lectureship of the American Astronomical Society (1958)

Named after him

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

See also

• 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.

References

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

• Osterbrock, Donald E. Walter Baade: A Life in Astrophysics. ISBN 0-691-04936-X. 

• Dieke, Sally H. (1970). "Baade, Wilhelm Heinrich Walter". Dictionary of Scientific Biography 1. New York: Charles Scribner's Sons. pp. 352–354. ISBN 0-684-10114-9. 

External links

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

Obituaries

• AN 285 (1960) 286 (one sentence, in German)
• JRASC 55 (1961) 113
• MitAG 14 (1961) 5
• Obs 80 (1960) 166 (one sentence)
• PASP 72 (1960) 434 (one paragraph)
• QJRAS 2 (1961) 118