James Kemp

(1927-1988)
James C. Kemp
Physicist & Professor

Inventor of the PEM and Initiator of So Much Relevant Research

Professor James Kemp, physicist at the University of Oregon, developed photoelastic modulators (PEMs) in the late 1960s for the advanced measurement of a wide range of polarization properties important to academic and industry researchers and professionals worldwide. Professor Kemp used the PEM to measure the polarization of light emitted from stars, thereby proving the existence of magnetic “white dwarf” stars.

This discovery provided the evidence used to award the Nobel Prize in physics to an astronomer at the University of Chicago (Chandraheskar) who had predicted the existence of such stars more than 40 years earlier.

James C. Kemp

James C. Kemp was born in Detroit, Michigan, on 9 February 1927, and died of cancer in Eugene, Oregon, on 29 March 1988 after a distinguished career as a physicist and astronomer.

His first degree was in Slavic languages. In 1960 he completed a PhD in electrical engineering at Berkeley, under Jerome R. Singer. Immediately thereafter, he joined Erwin Hahn in the physics department at Berkeley, to work on spin resonance. In 1961 Kemp came to the University of Oregon. For the remainder of the decade he and his students were engaged in magneto-optical studies of color centers in alkaline-earth oxide crystals. In 1969 he developed a piezo-optical birefringence modulator that allowed rapid and convenient measurement of circularly polarized light. This device played a crucial role in his subsequent development as an astrophysicist.

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In 1970 Kemp used his polarimeter to infer the magnetic field of the white dwarf star in Draco. His data, taken at the University of Oregon’s Pine Mountain Observatory, indicated a field of 1-3 XlO7 gauss, which could only be generated by the collapse of a normal star to a white dwarf. It was the first determination of the magnetic field of a white dwarf. The success of this measurement was characteristic of Kemp’s scientific style: making novel instruments (often by himself in the student machine shop) and using them to make significant new discoveries, possibly in a field far from his original interests.

His early success with the magnetic field measurements led Kemp to reduce his research in condensed matter physics and take an increasing interest in astrophysics, using the 61-cm reflector at Pine Mountain Observatory. He began a series of systematic observations on the black- hole binary Cygnus X-l. Soon he was able to convince the State to install an 81-cm reflector, which has remained the largest instrument at Pine Mountain. Indeed Kemp was a champion of small observatories and telescopes, dedicated to long-term programs of observation. At the time of his death, Kemp had accumulated 14 years’ worth of data on Cygnus X-l and had produced over 50 papers on astronomy.

Kemp was very much a rugged individualist, fond of appearing at all times wearing sandals and smoking a corncob pipe. He was often totally absorbed in his research and would pursue his goals regardless of obstacles.

I recall one occasion when, visiting Pine Mountain Observatory one summer evening, I was startled to see a substantial crowd of visitors just at sunset. Although he was eager to start that evening’s observations, Jim was explaining to all those assembled just what he was about to do and why, in a clear and enthusiastic manner that left every visitor, I believe, with an increased awareness of the scientific purpose of the observatory. On other occasions, when his research was going well, Jim would come to my office full of enthusiasm to describe what it was all about. His ideas and experiments were characteristically bold.

Kemp’s devotion to research was rivaled by his devotion to Pine Mountain Observatory. Pine Mountain is located near the center of Oregon and is reached by a strenuous four-hour drive over the Cascade Mountains. It was originally built as a summer observing station, but Kemp operated the observatory on a year-round basis. This required an almost continuous commuting routine through the hazards of fog, rain, snow and ice. He and his wife, Sarah van Riper, founded a support group named Friends of Pine Mountain Observatory, which has provided important public and financial support for research at the observatory for many years.

RUSSELL J. DONNELLY
University of Oregon
Eugene, Oregon

This article may be downloaded for personal use only. Any other use requires prior permission of AIP. This article appeared in Russell J. Donnelly; James C. Kemp. Physics Today 1 December 1989; 42 (12): 94–95. and may be found at https://doi.org/10.1063/1.2811257. Reproduced with the permission of the American Institute of Physics.

James C. Kemp

Professor James Kemp, Ever-Curious Astrophysicist

Not too long into his 27-year tenure at the University of Oregon Physics Department, Jim Kemp formed a support group to help provide both community and financial support for the University’s central-Oregon based Pine Mountain Observatory. Friends of Pine Mountain Observatory (FOPMO) grew quickly into an active support group, fueled by Kemp’s eager curiosity for all things astronomical. This fueled an increased awareness of the observatory throughout the region. Particularly in summer months, steady streams of both amateur astronomers and beginning-level, curious tourists from cities and towns far and wide throughout the Northwest and beyond headed to the 6300 ft. elevation of the observatory to look through the numerous telescopes into the dark sky of Central Oregon.

Everyone who was involved, whether as a curious, first-time-to-the-observatory tourist or as an involved FOPMO board member, was directly or indirectly influenced by Dr. Kemp’s infectious scientific curiosity. Below is a paragraph from the minutes of a board meeting on April 13, 1985 in which Kemp shared with the board an exciting new research project he and his assistants were working on.

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“New Project: A polarimetric planet search. This project has been on my mind for years, and at last we have started on it. Planets orbiting around stars produce polarized light, due to reflection of the star’s light. Jupiter-sized planets some 30 million miles from a star would cause a polarization of about 1 part in a million, in the total light from the star plus planet. With a recent improvement in the polarimeter on the 24” telescope, such detection is now in our range. We begin with the bright stars Vega and Regulus, and will later add Altair and other bright stars. Ten nights’ data on Vega are already slightly exciting – we may have already detected “something” going around Vega, emitting variable, reflected light. But we are settling down to many months of work on this project. The 32” telescope’s polarimeter, temporarily in the shop for improvements, will be brought into this project also, by summer.”