Stanton Jerrold (Stan) Peale, who made important contributions to an array of subfields in astronomy, from the theory of spin and orbital dynamics of solar system bodies to microlensing searches for exoplanets, died of leukemia on 14 May 2015 at age 78. Born in Indianapolis, Indiana, on 23 January 1937, Peale was the youngest of five children of Robert F. and Edith Mae Murphy Peale. He graduated from Indiana’s Southport High School in 1955 and went on to receive his B.S. degree in Engineering Sciences with highest distinction from Purdue University in 1959. Peale obtained his M.S. in 1962 and his Ph.D. in 1965 in astronomy from Cornell University. His thesis, conducted under the supervision of Cornell astronomer Thomas Gold, was titled “The Dust Belt of the Earth and the Zodiacal Light.”
In September 1965, after a brief stint as a research associate at Cornell's Center for Radio Physics and Space Research, Peale accepted a position as an assistant professor in the Department of Astronomy and the Institute of Geophysics and Planetary Physics at the University of California Los Angeles. Three years later, to escape the Los Angeles smog, he transferred to the Department of Physics at the University of California Santa Barbara, a position he held until his retirement as professor emeritus in 1994. During his tenure, the UCSB physics department doubled in size and rose to national prominence. In retirement, he continued his research and mentored postdoctoral fellows until shortly before his death. Combining an encyclopedic knowledge of physics with remarkable physical intuition, Peale wrote over 100 papers during his career, with more than 4,200 citations.
Among his significant papers are “Spin-Orbit Coupling in the Solar System,” with Peter Goldreich (Astronomical Journal, 1966), which explains, among other things, why Mercury's rotation period stabilized at two-thirds of its orbital period; "Rotation of Solid Bodies in the Solar System" (Reviews of Geophysics and Space Physics, 1973), which details the effects of elastic distortion, non-principal axis rotation, precessing orbits, and internal dissipation on the rotation of a solid solar system body in the gravitational field of an exterior body; “Determination of Parameters Related to the Interior of Mercury,” (Icarus, 1972); plus his 1976 letter to Nature, “Does Mercury have a Molten Core?”
Peale was a posthumous recipient of the 2016 Kuiper Prize, awarded by the AAS Division for Planetary Sciences to recognize and honor outstanding contributors to planetary science. In his letter of support for Peale’s nomination, colleague and friend Jean-Luc Margot wrote: “Stan’s early work on the spin state of Mercury is quite elegant. Stan wrote down the Hamiltonian describing a general planet-satellite (or sun-planet) system and arrived at generalized laws governing Cassini states. From there, he quickly realized that the determination of spin state parameters could provide important bounds on interior parameters, including the size and state of the core. This body of work underpinned and motivated the MESSENGER mission [to Mercury].” Peale also published a timely prediction of widespread volcanism on Jupiter's moon Io due to tidal dissipation. He later helped pioneer the study of extrasolar planets, both in terms of their dynamics and their detection by microlensing.
Sean Solomon, MESSENGER team member, added that “Much of our understanding of the interior structure of Mercury is the result Stan's innovative theoretical work, which spans more than four decades. Stan's most recent contribution to the literature on Mercury's interior was submitted to a journal just this Monday [11 May 2015, three days before his death].”
Peale was named a Fellow of the American Association for the Advancement of Science in 1981 and a Fellow of the American Geophysical Union in 1988. He received the Newcomb Cleveland Prize of the American Association for the Advancement of Science in 1979, NASA Exceptional Scientific Achievement Medal in 1980, James Craig Watson Award of the National Academy of Sciences in 1982, Dirk Brouwer Award of the Division of Dynamical Astronomy of the American Astronomical Society in 1993, and membership in the National Academy of Sciences in 2009. Asteroid 3612 was named after him in 1988.
Stan Peale met his future wife of 54 years, Priscilla L. Cobb, in 1959 at Cornell; they were married in Boston on 25 June 1960. Sons Robert and Douglas were born in Ithaca, New York, in 1961 and 1963, respectively. Peale was a hard-core bicycle commuter, and resumed his high-velocity pedaling in the wake of two serious encounters with automobiles that landed him in the hospital. As his colleague, Alan Boss, remarked, “He was not the type to give up easily on a scientific problem, or on his daily routine.” Peale was also an avid swimmer, both in the Pacific and in the UCSB campus pool.
In his Kuiper Prize Lecture at the 48th DPS meeting in October 2016, Jean-Luc Margot summed up his mentor’s legacy as a scientist and a person: “Stan reminded us that excellence is compatible with courtesy, generosity, and kindness."
— Alan Hirshfeld, with the assistance of Jean-Luc Margot, Alan Boss, and numerous colleagues of Stan Peale.
Photo credit: Henry Throop (Planetary Science Institute)