Walter Baade


Wilhelm Heinrich Walter Baade was a German astronomer who worked in the United States from 1931 to 1959.

Early life and education

Baade was born as 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.

Career

Baade worked at Hamburg Observatory at Bergedorf from 1919 to 1931. 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 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, to resolve stars in the center of the Andromeda Galaxy for the first time. These observations led him to define distinct "populations" for stars. 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. 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. Zwicky and he also proposed the existence of neutron stars, and suggested supernovae might create them.
Beginning in 1952, he and Rudolph Minkowski identified the optical counterparts of various radio sources, including Cygnus A. He discovered 10 asteroids, including 944 Hidalgo, which has a long orbital period ; the Apollo-class 1566 Icarus, the perihelion of which is closer than that of Mercury; and the Amor-type 1036 Ganymed.

Personal life

He died in 1960 in Göttingen, West Germany.

Honors

Awards
Named after him
Category:1893 births
Category:1960 deaths
Category:20th-century German astronomers
Category:German emigrants to the United States
Category:Discoverers of asteroids
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Category:Members of the Royal Netherlands Academy of Arts and Sciences
Category:Recipients of the Bruce Medal
Category:Recipients of the Gold Medal of the Royal Astronomical Society
Category:Members of the Göttingen Academy of Sciences and Humanities
Category:Academic staff of the University of Hamburg
Category:International members of the American Philosophical Society
Category:Discoverers of astronomical objects