Mathematics – Logic
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011baas...43..038d&link_type=abstract
Bulletin of the American Astronomical Society, Vol. 43, id. #038
Mathematics
Logic
Scientific paper
Allan Rex Sandage died of pancreatic cancer at his home in San Gabriel, California, in the shadow of Mount Wilson, on November 13, 2010. Born in Iowa City, Iowa, on June 18, 1926, he was 84 years old at his death, leaving his wife, former astronomer Mary Connelly Sandage, and two sons, David and John. He also left a legacy to the world of astronomical knowledge that has long been universally admired and appreciated, making his name synonymous with late 20th-Century observational cosmology.
The only child of Charles Harold Sandage, a professor of advertising who helped establish that academic specialty after obtaining a PhD in business administration, and Dorothy Briggs Sandage, whose father was president of Graceland College in Iowa, Allan Sandage grew up in a thoroughly intellectual, university oriented atmosphere but also a peripatetic one taking him to Philadelphia and later to Illinois as his father rose in his career. During his 2 years in Philadelphia, at about age eleven, Allan developed a curiosity about astronomy stimulated by a friend's interest. His father bought him a telescope and he used it to systematically record sunspots, and later attempted to make a larger 6-inch reflector, a project left uncompleted. As a teenager Allan read widely, especially astronomy books of all kinds, recalling in particular The Glass Giant of Palomar as well as popular works by Eddington and Hubble (The Realm of the Nebulae) in the early 1940s. Although his family was Mormon, of the Reorganized Church, he was not practicing, though he later sporadically attended a Methodist church in Oxford, Iowa during his college years.
Sandage knew by his high school years that he would engage in some form of intellectual life related to astronomy. He particularly recalls an influential science teacher at Miami University in Oxford, Ohio named Ray Edwards, who inspired him to think critically and "not settle for any hand-waving of any kind." [Interview of Allan Rex Sandage by Spencer Weart on 22 May 1978, Niels Bohr Library & Archives, American Institute of Physics, College Park, MD, USA, www.aip.org/history/ohilist/ and http://www.aip.org/history/ohilist/4380_1.html] Allan enrolled in Miami University in 1943 because his father was on the faculty there at the time. He majored in physics until he entered the Navy for 18 months to train as an electronics technician's mate. His training began in Chicago, where he became acquainted with others interested in astronomy, like Arthur Code and Albert Wilson, and then his tour took him to Gulfport, Mississippi, and finally to Treasure Island in the San Francisco Bay.
When Sandage was discharged from the Navy his father was moving to the University of Illinois, so Allan transferred there, entering a much larger and more competitive physics department. He majored in physics and mathematics but he also minored in philosophy, and took a celestial mechanics course from Robert H. Baker. He volunteered to work at the observatory, learning the art and craft of calibrating photographic plates so that magnitudes could be transferred and intercompared from plate to plate, an experience that he later realized prepared him well for his life career and also introduced him into Bart Bok's "star counting" circuit based at Harvard. In consequence, when Bok visited Illinois sometime in 1947, he invited Sandage to work at Harvard in their summer school at the Agassiz Station mapping Milky Way fields.
Sandage applied both to Harvard and Caltech for graduate school. Harvard was very well established in its graduate program whereas Caltech was just beginning to offer the Ph.D. in astronomy. He chose Caltech because that was where the big telescopes were. His family had visited Mount Wilson in 1941 during a summer when his father was teaching at Berkeley, and since that time Sandage had dreamed of observing with those giant telescopes.
Thus in September 1948, Sandage joined the first class of students to engage in formal graduate work at Caltech under the direction of Jesse Greenstein, who had been recruited from Yerkes for the purpose of establishing a Ph.D. program. Together with Halton C. Arp, Helmut Abt, and Morton Roberts, Sandage learned stellar atmospheres, interiors and the interstellar medium under Greenstein, along with relativity from H. P. Robertson and quantum mechanics from Richard Feynman. His first research paper, guided by Greenstein, utilized equivalent width data by R. B. King at Mount Wilson to explore the effect of temperature stratification in the solar atmosphere.
It did not take long before Sandage found a path to the big telescopes. Edwin Hubble had approached Greenstein to recommend a student who might provide assistance determining the distribution of galaxies in deep space with plates then being taken with the newly opened 48-inch Schmidt at Palomar. As Ira Bowen reported in his 1949 director's report, Hubble, "with the assistance of A.R. Sandage, is studying on some of these plates the distribution of faint nebulae in standard apparently normal regions of the sky." [Bowen, PASP 61 (1949), 250.] In the first year, Sandage's efforts were limited to processing Hubble's plates at Santa Barbara Street, but when Hubble suffered a massive heart attack on vacation in 1951, Sandage took over securing the fields with the Schmidt, trained carefully by Milton Humason. Upon Hubble's death in 1953, Sandage assumed the mantle.
As Sandage searched for a thesis topic in 1951, Hubble had no specific problems at hand that were appropriate, so Walter Baade agreed to take him on. Baade had trained both Sandage and Arp on securing photometric data on globular clusters with the Mount Wilson 60-inch, and now, teamed with William Baum, who was adept in the new photoelectric photometry, the three began pushing deeper to reach the main sequences of globular clusters, something no one had yet seen. M92 was their first target, and then Sandage took on M3 for his thesis. Together these efforts revealed the main-sequence turnoffs for the first time, and within a short time, in collaboration with Martin Schwarzschild at Princeton, they began to realize that cluster ages were on the order of at least 3 billion years, which agreed far better with geological time estimates for the earth's age than did Hubble's expansion value of 1.8 billion. This was also the beginning of the realization that red giants were evolved main-sequence stars, which was to become a hallmark of team work in modern astronomy at the observational-theoretical interface, centered around young astronomers like Sandage who were nurtured by Schwarzschild and Baade.
Throughout the 1950s Sandage worked along two major lines: revising and refining the Hubble Constant and clarifying the observational evidence for relative cluster ages, adding open clusters to create a powerful composite portrait of the migration of turn-off points down the HR diagram with advancing cluster age. These composite cluster diagrams provided new physical insights into the evolution of luminosity functions and many of the quirky characteristics of color magnitude diagrams. In collaboration with Olin Eggen and Donald Lynden-Bell, in the late 1950s through the early 1960s Sandage also formulated a collapse scenario for the evolution of the Milky Way, in a defining paper that has thus far garnered over 1400 citations. This was an important factor to consider in meeting his primary goal, to extend the Hubble diagram deep enough into space and time to be able to discriminate between various contending models for the history of the universe: its overall geometry and whether the expansion was constant, speeding up, or slowing down. Any evolutionary scenario for galaxies themselves would alter their observed characteristics, and hence influence one of the many distance indicators that had been devised by Hubble and those following him. Thus his efforts at establishing the Hubble Constant in following years included a staunch defense of a particular evolutionary scenario for galaxies that envisioned no observable changes in
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