| Activity | Education:
Sandage received a bachelor’s degree in physics from the University of Illinois at Urbana (1948) and a doctorate in astronomy from the California Institute of Technology at Pasadena in 1953. His adviser was Walter Baade.
Career:
While in graduate school, he was the observing assistant for American astronomer Edwin Hubble from 1950 until Hubble’s sudden death in 1953. 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 age of the Universe, to approximately 5.5 billion years[3]. 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 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 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", he discussed the future of observational cosmology as the search for two parameters - the Hubble constant Hn 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 and in 1981 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.
Following Hubble's death in 1953 Sandage continued with Hubble's passion to study the expansion of the universe. Periodically (with Gustav Tammann) he has updated the estimated value of the Hubble constant. Further, he has tried to establish a value for the deceleration parameter.
Seeking to determine the age of the oldest objects known, he has measured the ages and evolution of globular clusters. He has also calibrated the "standard candles" used to establish the distances of remote galaxies. As a result of his work in observational cosmology, the age of the universe has been measured progressively more accurately through the past decades.
In 1960, Dr. Allan Sandage made the first optical identification of a quasar, with his junior colleague, Thomas Matthews. He had found that there was a faint optical object with an extraordinary spectrum at the position of the compact radio source 3C 48 in the constellation Virgo. This faint quasi-stellar object was emitting more intense radio waves and ultraviolet radiation than a typical star. (Following this discovery, in 1963, Maarten Schmidt explained the unusual spectrum as due to a huge red-shift of the hydrogen lines. This suggested the quasar was moving exceptionally fast (30,000 miles per second) and therefore was extremely distant (3 billion light-years away) and luminous as hundreds of galaxies.)
Subsequently Sandage has documented many more quasars, finding they are predominantly "radio-quiet" (99%).
Following research interests in stellar evolution, observational cosmology, quasars, and galaxy formation and evolution, Sandage has been prolific. He has published more than four hundred research papers, is author of five books, with more activity as Associate Editor of the Annual Review of Astronomy and Astrophysics.
Staff Astronomer, Carnegie Observatiories, California USA. Astronomer Emeritus, The Observatories of the Carnegie Institution of Washington, Carnegie Observatories, USA
Medals and Awards
Helen B. Warner Prize for Astronomy (1957); Eddington Medal (1963); Gold Medal of the Royal Astronomical Society (1967);
National Medal of Science (1970) ; Henry Norris Russell Lectureship (1972); Elliott Cresson Medal (1973); Bruce Medal (1975)
Crafoord Prize (1991)
Named after him; Main-belt asteroid, 9963 Sandage (1992 AN)
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