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William Albert Hiltner was born on August 27, 1914 on his parents' farm in North Creek, Ohio, some 45 miles southwest of Toledo. He received his early education in the one room school house that served this farm community. Al acquired his interest in astronomy while still very young, apparently from an amateur astronomer who lived near the family farm. He purchased a small telescope and was disappointed when he found that Vega still looked like a "star" despite the magnification afforded by the telescope. Al graduated from a small high school in a graduating class of 17 in 1932. The following year he entered the University of Toledo where he majored in physics and math. It was in his senior year that he decided to make astronomy his life work. Commenting on that choice many years later Al said "One makes a decision to do astronomy when one is helpless to prevent it!"
He received his Bachelor of Science degree from the University of Toledo in 1937 and started graduate studies in astronomy at the University of Michigan. This was not the end of his interest in Toledo, where he frequently spent his weekends until he married Ruth Kreider, a former classmate. He returned again to Toledo thirty years later to accept an honorary DSc. degree from this, his first alma mater. At the University of Michigan Al obtained an MS degree in 1938 and a PhD in astrophysics in 1942. His thesis research was on the spectra of Be stars, with emphasis on determining color temperatures through accurate spectrophotometry. For this research he and Robley Williams constructed the University of Michigan microphotometer. Later they published the Photometric Atlas of Stellar Spectra. As a National Research Council Fellow he continued his association with the University of Michigan and observed and carried out a productive research program at McDonald Observatory. In 1943 he was appointed an Instructor at Yerkes Observatory and he and his family. which now included two daughters, moved to Yerkes Observatory in Williams Bay Wisconsin, a village only slightly larger then North Creek, Ohio. During the early days at Yerkes he continued his spectroscopic studies of Be stars and some of the other pathological cases that had been Otto Struve's favorites.
During World War II Al was engaged in the production of front surface mirrors, and in military optics design and modeling, an experience which influenced his later interest in astronomical instrumentation. It was following the end of the war that I came to Yerkes Observatory as a graduate student and had the opportunity to work with AI on two projects. Otto Struve had suggested that AI develop a program in photoelectric photometry at Yerkes and I was appointed his assistant. We started with a simple system employing a sensitive galvanometer to record the output of a photomultiplier. It was my task to sit near the 40 inch pier, in the basement, in front of the galvanometer scale. From the observing floor above AI would call out the instructions to read the position of the dancing spot of light on the scale. From this humble beginning AI brought photometry and later polarimetry and electronic imaging at Yerkes into the modern era.
In 1945 Hiltner and Chandrasekhar went to Canada to photograph a total eclipse of the sun. This represented a unique collaboration with the theorist Chandrasekhar, for I believe that the paper showing those photographs remains the only observational research paper ever published by Subrahmanyan Chandrasekhar. Another interaction between Chandra and AI, however, had a much greater impact on astronomy. Chandrasekhar had predicted that when electron scattering was the dominant contributor to the stellar opacity the limb intensity would show linear polarization reaching 11 % for pure electron scattering. AI set out to measure this polarization in eclipsing binary systems. He found polarization, but it did not change with binary phase. Indeed many early type stars showed polarization in the several percent range. As the data collected, it became clear that the polarization was produced in the interstellar medium. In 1949, in back-to-back papers in Science, Al Hiltner and John Hall announced the discovery of interstellar polarization. Interstellar polarization gave the first evidence for galactic magnetic fields and a powerful diagnostic on the nature of interstellar grains.
Over the years AI published over 200 papers in scientific journals. While he continued measurements of polarization, photometry and spectral classification of early type stars he was most interested in binary stars. He made valuable contributions to our understanding of Wolf-Rayet binaries, and after the discovery of x-ray binaries he turned his attention to the study of the optical radiation from these x-ray sources. He enjoyed sharing this research with students and young astronomers and imparting to them the enthusiasm that he himself had for scientific inquiry.
As AI progressed through the ranks from Instructor to Professor at the University of Chicago, he took on increased responsibilities as both an instrument innovator and policy maker. Starting in 1959 and continuing until his departure from Yerkes Observatory in 1971, he was the University of Chicago's representative on the Board of Directors of AURA The facilities which now cover the summit of Kitt Peak owe much to the efforts of the early Board members. He played an important role in the development of the Cerro Tololo Interamerican Observatory in Chile. In 1966 CTIO was without a director and AI served as one of the interim directors until the appointment of Victor Blanco in 1967. He also served as President of AURA from 1968 through 1971. His departure from the Board following his term of office was a result of his departure from Yerkes Observatory after 27 years of productive and diverse activity.
Al returned to the place where he had received his training in 1970 to become chairman of the Department of Astronomy at the University of Michigan. His ability to imagine and to make things happen led to a fruitful collaborative agreement between Michigan, Dartmouth and MIT. The MDM consortium started with the move of the Michigan 1.3 meter telescope and later the construction of a 2.4 meter telescope, which was designed by AI and now bears his name.
When AI retired from the University of Michigan in 1985 it was not just be a professor emeritus but rather to take on a new challenge. The Carnegie Institution had embarked on a collaborative effort to produce a very large southern hemisphere telescope. In 1986 AI joined the staff of the Carnegie Observatories to become the Project Manager for the Magellan Telescope Project a program to build an 8-meter telescope to be place in Chile.
One of the characteristics which his younger colleagues have remarked on was his ability to keep up-to-date, to keep learning. and as such it was not at all remarkable that he had been chosen to head the Magellan Project. This characteristic, however, applied to his personal as well as his professional life. During his years at Yerkes Observatory he enjoyed sailing on Lake Geneva and canoeing with the family in northern Wisconsin in spite of the fact that he had not learned to swim in his youth. He did learn to swim, however, at the age of 64 and took great pride in that accomplishment, which he enjoyed the rest of his life.
For the last ten years of his life AI had been under the care of a cardiologist for a deteriorating heart condition. He had resisted surgery until finally in September of 1991 he decided to risk surgery as a last resort. They were unable to get his heart to beat on its own after removing the support system. He is survived by his wife Ruth. and four children, two sons and two daughters.
Al was a great success as a scientist, a teacher, a builder, and a scientific leader, and went out of his way to instill these attributes in the younger astronomers who had the opportunity to work with him.
Photo (available in PDF version) Dr. W. A. Hiltner, Pasadena, CA 1987, by Steven Padilla, Observatories of Carnegie Institute of Washington.
Obituary written by: Arthur D. Code (University of Wisconsin)
BAAS Citation: BAAS, 1992, 24, 1326
SAO/NASA ADS Bibcode: 1992BAAS...24.1326C