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Richard Nelson Thomas (1921–1996)

Published onSep 01, 1996
Richard Nelson Thomas (1921–1996)

Richard Thomas died in his sleep at his home in Boulder, Colorado the night of Monday, April 8-9. Dick had suffered a stroke during surgery in the spring of 1992, and struggled courageously with the subsequent partial paralysis for the next four years, always keeping his interest in astronomy, astronomers and his family foremost among his thoughts. He is survived by his wife, Nora, their step-daughter, Anush, and his daughter, Bess Alta.

Dick was born in Omaha, Nebraska on 3 March 1921 to Joseph Francis Thomas, lawyer and businessman, and to Mabel (née Nelson) Thomas. He attended high school in Omaha, where he was a top debater and wrestler, and continued to excel in both as he entered Harvard in 1938. Dick planned to become a chemical engineer, but after taking courses from Cecilia Payne-Gaposchkin and Donald Menzel he switched to astronomy. He was excited by the application of the Saha equation to spectral classification and the emergence of a formalism for treating processes in planetary nebulae far from a state of thermodynamic equilibrium. He received his Bachelors degree in physics from Harvard in 1942 and his PhD in astrophysics in 1948 working with Menzel, with a thesis on "Superthermal Phenomena in Stellar Atmospheres."

During World War II Dick served at the Army Ballistics Laboratory in Aberdeen, Maryland. His military duty contributed to his lifelong interest in stellar winds, as demonstrated by photographs of supersonic and hypersonic shock patterns taken at Aberdeen that appear in his last book. In 1949, Dick moved to the University of Utah, where astrophysicist Eugene Parker was one of his colleagues and Grant Athay one of his first graduate students. During this period he began a highly productive collaboration with Athay and Jean Claude Pecker, who in 1952 participated in a now famous eclipse expedition to Khartoum. This expedition provided the necessary observations to test and confirm Dick's ideas on strong departures from thermodynamic equilibrium in the solar chromosphere. As a result of this work, he and Athay edited The Physics of the Solar Chromosphere (1961), one of the best known books on the subject. It had a profound influence on the development of non-LTE theory for the analysis of stellar spectra.

Following his years in Utah, working again at Harvard and then at the High Altitude Observatory and the Bureau of Standards in Boulder, Colorado, Dick and others conceived the plan for what was to become The Joint Institute for Laboratory Astrophysics (JILA). Discussions with Bureau scientist Louis Branscomb, former Bureau Head Ed Condon and members of the Boulder scientific community led to the creation of JILA in 1962 as a joint Bureau/University of Colorado institute for the pursuit of research and teaching that has since gained a worldwide reputation.

Dick began the JILA Visiting Fellows Program which brought many distinguished astrophysicists to Boulder over the past 30 years. Directly or indirectly, he was also responsible for building up the JlLA staff. For his services to astronomy and to the Bureau in helping to establish JlLA, Dick received the Gold Medal for Exceptional Service from the United States Department of Commerce in 1963.

Dick served as President of the IAU Stellar Atmospheres Commission in the early 1970s and was a prime mover behind and the editor for a series of international symposia on Cosmical Gas Dynamics. He was Foreign Correspondent of Annales d'Astrophysique, an editor for The Physics of Fluids, a member of the RAS and a Corresponding Member of the Société Royale des Sciences de Liège. Other academic appointments included an adjunct professorship at the University of Colorado and visiting professor at the University of Paris both beginning in 1961, and, later, visiting professor at the College de France.

After a decade with JlLA, in 1973 Dick joined the staff of the Institut d'Astrophysique in Paris, at the behest of Jean-Claude Pecker. Since the 1950s they both insisted on the application of non-LTE to solve a number of hitherto puzzling problems in interpreting solar spectra, and contributed to making non-LTE theory the standard tool for analyzing most stellar spectra, especially those spectra formed in the low-density outer regions of the chromosphere and the corona.

In Paris Dick commenced the final major project of his life, a monograph series on nonthermal phenomena in stellar atmospheres, backed by the French CNRS and by NASA. Leo Goldberg and Pecker were the senior advisers, and I became the NASA coordinator for the project. This project produced eight volumes covering the Hertzsprung-Russell Diagram, and were made available to astronomers the world over, receiving excellent reviews. Dick contributed Stellar Atmospheric Structural Patterns, a book that was vintage Dick Thomas: hard to read, full of fresh suggestions, and challenging to much conventional thinking on stellar atmospheres. Dick's last major scientific interest was the origin of stellar winds. He was convinced that there was a common primary driver, or source, of stellar winds for all stars, although he acknowledged some important differences between the 'early' and 'late' type stars, differences that he nonetheless regarded as secondary rather than fundamental in producing their corresponding winds. His approach was to look for statistical fluctuations and new sources mass-loss. So far this idea has not met with empirical validation or widespread acceptance, especially since some of the problems Dick was addressing seem to have found at least partial solution through more conventional approaches. Nevertheless, he continued to play the role of constructive gadfly to those who accepted conventional wisdom all too easily. And there were always a few outstanding astrophysicists who, however bizarre some of his ideas seemed at first, felt compelled to ask themselves "Dick was often right before. Why would he propose that?"

In some ways Dick was superseded by the modern era in astronomy. He never learned to appreciate the full power of the computer to advance the field, and often failed to work through the detailed consequences of his own ideas. However, in an era when cleverness and technique had arguably come to dominate much scientific endeavor, Dick continued to work in the honorable tradition of testing fundamental ideas.

Dick was always stimulating, but not always easy to work with. In his own way he was quite thoughtful, but often after the fact. Anyone working with Dick had to be prepared to occasionally say No! to him quite firmly, and to make it stick. He believed that he was a good manager, yet often had difficulty implementing his projects without others to run interference, not unlike a fine running back who still needs a few good blockers along the way. Yet he was often extremely generous in praising the contribution of others, especially those who had helped him in his work.

Aside from his speculative work on stellar winds, Dick's major role in developing the theory for treating optically thick spectral lines in a stellar atmosphere puts him in the front rank of astronomers. Interpretation of observations from all space observatories operating in the near and far ultraviolet, and from a host of ground-based observatories, has been greatly advanced by this fundamental work. And no one was more energetic in disseminating these results globally.

To anyone who showed a strong interest in, or a talent for, astronomy, Dick's office and home were always open. In many cases, he helped struggling young researchers directly, finding them positions and occasionally direct grants. If Dick could be brusque, it was invariably in a sincere effort to advance astronomy and astronomers. In moments of relaxation he could be the most charming of hosts and the most helpful of friends. Personally, he was wonderfully stimulating, and will be remembered for his talent for incisive innovation, sincerity, professional courage, and absolute dedication to astronomy. In life we often reward reasonable accommodation, less often obstreperous individualism, even when it is highly productive.

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