Nov. 26, 2008

Edwin Salpeter, whose theories revolutionized astrophysics, dies at 83

Eminent astrophysicist Edwin Salpeter, a seminal figure in theoretical physics whose research encompassed black holes and missile defense systems, died Nov. 26 of leukemia at his home in Ithaca, N.Y. He was 83.

At his death, Salpeter was the J.G. White Distinguished Professor of Physical Sciences Emeritus at Cornell University. A self-described "generalist" whose intellectual passions ranged widely, he tackled some of the most challenging problems in describing the physics of the universe during a career spanning more than half a century.

"More than any other individual, Ed put the physics into astrophysics,'' said Ira Wasserman, chairman of the astronomy department at Cornell. "Ed transformed our field forever.''

Salpeter's lasting contributions to the field of astrophysics include the "Salpeter process," which describes how helium nuclei fuse to form carbon in the interiors of ancient stars. Before Salpeter's discovery of this process, the origin of the elements beyond helium in the periodic table was a mystery.

A penetrating synthesis of observational data and theory enabled Salpeter to determine the numbers of stars of different masses that form in the Galaxy. This "Salpeter initial mass function" remains the basis for contemporary studies of the rates of stellar births and deaths.

A modest man with an infectious grin, Salpeter possessed great intuitive powers and a keen ability to visualize abstract theoretical concepts. With characteristic self-deprecation, he described his mind as "quick but sloppy" in that he preferred the challenges of describing a controversial new problem to undertaking mathematical calculations.

"Salpeter has made pivotal contributions to our understanding of a variety of very different fields in the study of the universe," said Andrew Franknoi, executive director of the Astronomical Society of the Pacific (ASP) in 1987, when Salpeter was awarded the ASP's prestigious Catherine Wolfe Bruce Medal in Astronomy. "He is especially admired by his colleagues for his physical intuition, which enables him to see to the heart of fundamental problems before beginning more detailed calculations."

Alan Lightman, theoretical physicist-turned-novelist and author of the best-selling novel "Einstein's Dreams," testified to Salpeter's intuitive genius: "When I was stymied by a tough astrophysics problem at Cornell, the great theoretician Edwin Salpeter, while lying on the floor of his living room with back pain, instantly drew an analogy between the slow drift of stars orbiting a disruptive mass and the random motion of marbles bumping around on a table with a hole in its center."

Like his mentor, the German-born Nobel laureate Hans Bethe, Salpeter fled his homeland -- in his case, Austria -- as the Nazis rose to power. In 1949 Salpeter traveled to Cornell as a young postdoctoral fellow to study with Bethe. He stayed at Cornell throughout his career. Although he claimed that he "essentially had only a single job" in his life, he worked in several different fields, even venturing outside of the physical sciences altogether to collaborate on medical research with his wife and daughter.

In 1964, Salpeter and Yakov Zeldovich of the Institute of Applied Mathematics in Moscow independently proposed that a stream of gas falling toward a black hole could in principle be heated to very high temperatures. Three decades later, data from the Hubble telescope conclusively demonstrated Salpeter's claims. "It's good to finally win the bet," said Salpeter upon learning of the Hubble findings in 1994.

Throughout much of his life, Salpeter was involved in public service, serving on the Space Science Panel for the President's Science Advisory Committee in the 1960s and on the National Science Board from the late 1970s to the early 1980s.

Salpeter also performed classified research for the Department of Defense in the 1960s, evaluating -- and mostly debunking -- claims made in favor of anti-ballistic missile defense systems.

In 1985, along with 16 other eminent physicists, Salpeter was appointed by the American Physical Society (APS) to a panel commissioned to study the feasibility of directed energy weapons systems such as the Reagan administration's proposed Strategic Defense Initiative, popularly dubbed "Star Wars." After two years of deliberation, the panel unanimously concluded that the claims made by SDI's proponents were inaccurate, and that the technology required to implement the "Star Wars" initiative did not yet exist.

"What is most spectacular is that 17 people with different political views unanimously agreed on one, single report," said Salpeter, who gained some notoriety by speaking out about what he called "gross dishonesty without outright lies" from the supporters of Star Wars.

Salpeter retired from Cornell University in 1997, but continued to publish papers and explore new avenues of research.

Late in his career, Salpeter became increasingly interested in neurobiology and epidemiology, collaborating with his wife, Miriam (Mika), professor of neurobiology and behavior at Cornell, on research into the interactions between nerves and muscle fibers. The Salpeters used supercomputer simulations of these interactions to study the deterioration of muscle function that occurs in victims of degenerative muscular diseases, such as myasthenia gravis. Upon Mika's death in October of 2000, he took over the running of her laboratory.

Salpeter also worked late in his life on the epidemiology of tuberculosis, in collaboration with his daughter, Shelley, a physician, and recently with his grandson, Nicholas Buckley.

To his medical research, Salpeter brought his keen ability to make theoretical connections between seemingly unrelated phenomena.

"My switch to epidemiology was not as radical a change as you might think," he said. "Humans coughing tuberculosis mycobacteria into the air at different ages required similar mathematical treatment to stars of different lifetimes disbursing heavy elements into the interstellar medium."

Salpeter was born Dec. 3, 1924, in Vienna, and was taken to Australia by his parents in 1939. He attended Sydney University, where he obtained his bachelor's degree in 1944 and his master's degree in 1945. In the same year he was awarded an overseas scholarship and attended Birmingham University, England, where he earned his doctorate in 1948.

Salpeter received many prestigious awards during his lifetime of groundbreaking work, including the Gold Medal of Britain's Royal Astronomical Society in 1973, the Royal Swedish Academy's $500,000 Crafoord Prize in 1997 (which he shared with British astronomer Fred Hoyle), and the APS Hans A. Bethe prize in 1999. He was awarded honorary doctorates by the University of Chicago, Case Western Reserve University, Sydney University and the University of New South Wales.

"Ed's contributions to astrophysics revolutionized whole subfields," said longtime colleague Saul Teukolsky, the Hans A. Bethe Professor of Physics and physics department chair at Cornell. "And yet no matter how eminent he became, Ed retained his humility and sense of fun. Colleagues visiting Cornell always wanted to talk to him, not just because he was a great scientist, but because it was truly a delight to spend time with him."

"I don't ever remember Ed working on a trivial problem," said colleague Yervant Terzian, the David C. Duncan Professor in the Physical Sciences at Cornell, speaking at a symposium in honor of Salpeter upon his retirement in 1997. "Ed is one of the most respected scientists in the world, and his unpretentious attitude has made him a great human being."

Salpeter is survived by his wife, Antonia "Lhamo" Shouse Salpeter; daughters Judy and Shelley; and four grandchildren.