James Wellington Truran

Astrophysicist James Wellington Truran, professor emeritus of astronomy and astrophysics at the University of Chicago, passed away on 5 March 2022 in Chicago. Throughout his career, Jim made far-reaching contributions to the theory of nuclear reactions, stellar nucleosynthesis, big bang nucleosynthesis, stellar abundances, solar system formation, galaxy formation, and galactic chemical evolution. He was a world leader in those fields, and his work influenced the direction of nuclear astrophysics for decades.

Born in Brewster, New York, on 12 July 1940, Jim received a bachelor’s in physics from Cornell University in 1961 and a master’s in physics in 1963, followed by a PhD in physics from Yale University in 1966, under the guidance of Alastair Cameron. Following the initial development of nuclear astrophysics by Margaret Burbidge, Geoffrey Burbidge, William Fowler, and Fred Hoyle, and Al Cameron’s contributions in 1957, Jim (along with other students of Cameron) led a new generation in developing novel ideas and techniques in astrophysics. Jim was the first to provide large-scale predictions for nuclear reaction rates used in studies of nuclear burning, the big bang, and stellar evolution and explosions. He also developed nuclear reaction networks and new computer techniques for nucleosynthesis studies, including pioneering explosive synthesis calculations.

After graduation, Jim worked as an NAS-NRC fellow at the NASA Goddard Institute for Space Studies from 1965 to 1967 and as a research fellow at Caltech from 1968 to 1969. In 1967 Jim became an assistant professor of space physics at Yeshiva University, where he became an associate professor in 1970 and a professor in 1972. From 1973 to 1991, Jim was a professor of astronomy at the University of Illinois Urbana–Champaign, before finally joining the faculty of astronomy and astrophysics at the University of Chicago.

Together with Icko Iben, Susan Lamb, and Mike Howard, Jim made important contributions to the understanding of stellar evolution and the s-process in stars, including the discovery of the weak s-process and its importance in the evolution of massive stars. Jim’s work on novae (with Sumner Starrfield and Warren Sparks, Mario Livio and Ronald Webbink, Jean Audouze, Ami Glasner and colleagues) includes many of the first reactive hydrodynamics simulations of the outbursts, which were crucial to accurate calculation of these dynamic events and to understanding their origin and onset.

Jim’s work with Dave Arnett and Stan Woosley in 1971 led to the first suggestion of carbon detonation models for type Ia supernovae. In recent years, Jim was deeply involved in the development of the multiphysics FLASH code at Chicago with a large group of collaborators and its application to modeling thermonuclear supernovae. Further extensions of this work led to an understanding of the variation in the predicted peak luminosity as a function of stellar metallicity. Most recently, Jim was deeply involved in investigating the possible origins of type Ia supernovae from He detonations on white dwarfs.

In the late 1970s, Jim became involved in a series of joint investigations with Cameron and John Cowan to understand the origin of the r-process, eventually extending into joint investigations with Wolfgang Hillebrandt’s group in Garching, Germany. Their collective work uncovered the critical roles of explosive He burning during supernova explosions, based on neutron production via the ¹³C(α, n) reaction, and of the high-entropy wind in core-collapse supernovae. Jim’s 1991 review article with Cowan and Friedrich-Karl Thielemann served for many years as a guide to understanding the general nature of the r-process. Continued collaboration of Jim with Cowan and Chris Sneden on r-process abundance observations in low-metallicity stars helped to provide further constraints on r-process sources to finally reach a full understanding of all stellar contributions.

Jim’s 1989 review article with Sneden and Craig Wheeler provided fundamental contributions to a modern understanding of galactic chemical evolution, relating the origins of, for example, C, N, and s-process elements; the alpha elements; and the Fe-group and r-process elements to their nucleosynthesis sites in low- and intermediate-mass stars, massive stars and their core-collapse supernovae, and type Ia supernovae. Those studies opened the path to the present understanding of galactic chemical evolution, including the signature of the first stars and the origin of the r-process, which would be unthinkable without Jim’s inputs.

Jim created an enormous scientific oeuvre, and the impact of his work on nuclear astrophysics is profound and extensive. His pioneering early studies spread into many related research areas. His ideas and his interactions with students and collaborators from all over the world deeply enriched the whole field of nuclear and computational astrophysics. Spending any amount of time with Jim discussing the history of nuclear astrophysics was always inspiring and an opportunity to learn about fundamental results from that history.

Among his many honors, Jim received a Guggenheim Fellowship in 1979– 80 and a Humboldt Research Award at the Max Planck Institute for Astrophysics in 1986–87 and 1989. He was a fellow of the American Academy of Arts and Sciences and the American Physical Society. More recently, in 2020 he was awarded the Prize of the Laboratory Astrophysics Division of the American Astronomical Society, and in 2021, the Hans A. Bethe Prize of the American Physical Society for “his distinguished contributions across the breadth of nuclear astrophysics, galactic chemical evolution and cosmochronology.” Throughout his career, he served the scientific community: Highlights include his membership in the HST (Hubble Space Telescope) & Beyond Committee, which received the Carl Sagan Memorial Award in 2017; his time as vice president of the Aspen Center for Physics; and his membership on its board of trustees.

Jim was admired by the many students and colleagues whose lives and careers he touched. He gave generously of himself as an adviser, role model, confidant, and friend. He stood out because of his character and kindness toward his many graduate students, postdocs, and collaborators around the globe. Jim was an outstanding teacher and mentor who had superb judgement, a quickness to grasp and thoroughly understand a problem, and an ability to convey more difficult concepts in an interesting and simple way. His intensity, clarity, careful preparation, and beautifully handwritten lecture notes captured the attention of his students, who recall his emphasis on fundamental principles and his insistence that they present their work clearly and logically. Jim treated everyone as an individual, each with his or her own strengths and weaknesses; he would encourage and praise everyone and spare no effort in helping them along the path of a scientific career. In his private life, he was a passionate tennis player and always supportive of his family. We will all miss his incredible enthusiasm, integrity, intuition, and most of all, his friendship.