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Allan Sandage
Born June 18, 1926 (1926-06-18) (age 83)
Iowa City, Iowa
Residence California, U.S.A.
Nationality American
Fields astronomy
Institutions Carnegie Observatories
Alma mater California Institute of Technology
University of Illinois
Doctoral advisor Walter Baade
Known for cosmology
Influences Edwin Hubble
Notable awards Bruce Medal 1975

Allan Rex Sandage (born June 18, 1926 in Iowa City, Iowa) is an American astronomer. He is Staff Member Emeritus with the Carnegie Observatories in Pasadena, California.[1] He is best known for determining the first reasonably accurate value for the Hubble constant and the age of the universe.

Asteroids discovered: 1
(96155) 1973 HA 27 April 1973

Contents

Career

Allan R. Sandage is one of the most influential astronomers of the 20th century. Sandage graduated from the University of Illinois in 1948. By 1953 he earned his Ph.D. from the California Institute of Technology with the German observational astronomer Walter Baade as his advisor. During this time Sandage was a graduate student assistant to the famed cosmologist Edwin Hubble. Sandage continued Hubble's research program after Hubble's sudden death in 1953. Throughout the 1950s and well into the 1980s Sandage was regarded as the pre-eminent observational cosmologist. Sandage has made seminal contributions to all aspects of the cosmological distance scale from local calibrators within our own Milky Way Galaxy to cosmologically distant galaxies.

Sandage began working at the Palomar Observatory. In 1958 he published[2] the first good estimate for the Hubble constant, revising Hubble's value of 250 down to 75 km/s/Mpc, which is quite close to today's accepted value. Later he became the chief advocate of an even lower value, around 50, corresponding to a Hubble age of around 20 billion years.

He performed photometric studies of globular clusters, and deduced that they had an age of at least 25 billion years. This led him to speculate that the Universe did not merely expand, but actually expanded and contracted with a period of 80 billion years. The current cosmological estimates of the age of the universe, in contrast, are typically of the order of 14 billion years. As part of his studies on the formation of galaxies in the early Universe, he co-wrote the seminal paper[3] now called ELS after the authors Olin J. Eggen, Donald Lynden-Bell, and Sandage first describing the collapse of a proto-galactic gas cloud into our present Milky Way Galaxy.

In his paper of 1961 "The Ability of the 200-inch Telescope to Discriminate Between Selected World Models"[4], he discussed the future of observational cosmology as the search for two parameters - the Hubble constant H0 and the deceleration parameter q0. This paper influenced observational cosmology for at least three decades as it carefully laid out the types of observational tests that could be performed with a large telescope. He also published two atlases of galaxies, in 1961[5] and in 1981[6], based on the Hubble classification scheme.

He is noted for the discovery in the M82 galaxy of jets erupting from the core. These must have been caused by massive explosions in the core, and the evidence indicated the eruptions had been occurring for at least 1.5 million years.[7]

He is a prolific researcher with over 500 papers. He continues to be an active researcher at the Carnegie Observatories and is showing no sign of retiring, still publishing several papers a year.[8]

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Honors

Awards

Named after him

References

  1. ^ "Carnegie Observatories - Pasadena". http://obs.carnegiescience.edu/personnel/contact/. Retrieved 2009-12-04.  
  2. ^ Sandage, A. R. (May, 1958). "Current Problems in the Extragalactic Distance Scale.". Astrophysical Journal 127 (3): 513-526. doi:10.1086/146483. Bibcode1958ApJ...127..513S.  
  3. ^ Eggen, O. J., Lynden-Bell, D., Sandage, A. R. (November, 1962). "Evidence from the motions of old stars that the Galaxy collapsed.". Astrophysical Journal 136: 748-766. doi:10.1086/147433. Bibcode1962ApJ...136..748E.  
  4. ^ Sandage, A.R. (March, 1961). "The Ability of the 200-INCH Telescope to Discriminate Between Selected World Models.". Astrophysical Journal 133 (2): 355-392. doi:10.1086/147041. Bibcode1961ApJ...133..355S.  
  5. ^ Sandage, A. R. (1961). The Hubble atlas of galaxies. Washington: Carnegie Institution. Bibcode1961hag..book.....S.  
  6. ^ Sandage, A.R., Tammann, G. A. (1981). A revised Shapley-Ames Catalog of bright galaxies. Washington: Carnegie Institution. Bibcode1981rsac.book.....S.  
  7. ^ Lynds, C. R.; Sandage, A. R. (May, 1963). "Evidence for an Explosion in the Center of the Galaxy M82.". Astrophysical Journal 137 (4): 1005-1021. doi:10.1086/147579. Bibcode1963ApJ...137.1005L.  
  8. ^ As shown with a SAO/NASA ADS search performed 2009-12-04.

Further reading

  • Alan P. Lightman and Roberta Brawer, Origins: the lives and worlds of modern cosmologists, Harvard University Press, 1990. Interviews with modern cosmologists, including Sandage.
  • Timothy Ferris, The Red Limit: The Search for the Edge of the Universe, Harper Perennial, 2002. Non-technical description of research, primarily up to about 1980, on cosmology; Sandage was a key figure, and features accordingly.
  • Dennis Overbye, Lonely Hearts of the Cosmos: the story of the scientific quest for the secret of the Universe, HarperCollins 1991, Back Bay (with new afterword), 1999. Very well-written historical account of modern cosmology told through the careers of the scientists involved, in which Sandage is the central character. Complementary to Origins.

External links


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