Allan Sandage
| Allan Sandage | |
|---|---|
 |
|
| Born |
June 18, 1926 Iowa City, Iowa |
| Died | November 13, 2010 (aged 84) San Gabriel, California |
| Nationality | United States |
| Fields | astronomy |
| Institutions | Carnegie Observatories |
| Alma mater |
California Institute of Technology University of Illinois |
| Doctoral advisor | Walter Baade |
| Known for | Physical cosmology |
| Influences |
Walter Baade Edwin Hubble |
| Notable awards | Helen B. Warner Prize for Astronomy (1957) Eddington Medal (1963) Rittenhouse Medal (1968) National Medal of Science (1970) Elliott Cresson Medal (1973) Bruce Medal (1975) Crafoord Prize (1991) Fellow of the Royal Society |
Allan Rex Sandage (June 18, 1926 – November 13, 2010) was an American astronomer. He was Staff Member Emeritus with the Carnegie Observatories in Pasadena, California. He determined the first reasonably accurate values for the Hubble constant and the age of the universe. He also discovered the first quasar.
Sandage was one of the most influential astronomers of the 20th century. He was born in Iowa City, Iowa, United States. He graduated from the University of Illinois in 1948. In 1953 he received a Ph.D. from the California Institute of Technology; the German-born Wilson Observatory-based astronomer Walter Baade was his advisor. During this time Sandage was a graduate student assistant to cosmologist Edwin Hubble. He continued Hubble's research program after Hubble died in 1953. In 1952 Baade surprised his fellow astronomers by announcing (at the 1952 Conference of the International Astronomical Union, in Rome) his determination of two separate populations of Cepheid variable stars in the Andromeda Galaxy, resulted in a doubling of the estimated age of the universe (from 1.8 to 3.6 billion years). Hubble had posited the earlier value; he had considered only the weaker Population II Cepheid variables as standard candles. After Baade's pronouncements, Sandage showed that astronomers' previous assumption, that the brightest stars in galaxies were of approximately equal inherent intensity, was mistaken in the case of H II regions which he found not to be stars and inherently brighter than the brightest stars in distant galaxies. This resulted in another 1.5 factor increase in the calculated age of the universe, to approximately 5.5 billion years. Throughout the 1950s and well into the 1980s Sandage was regarded as the pre-eminent observational cosmologist, making contributions to all aspects of the cosmological distance scale, ranging from calibrators within our own Milky Way Galaxy, to cosmologically distant galaxies.
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