Professor emeritus of physics George Whipple Clark PhD ’52, an astrophysicist who was a pioneer in X-ray and gamma-ray astronomy, died on April 6, 2023, in Boston. He was 94.
In the SAS-3 control room is (left to right) Bill Mayer, Jeff McClintock, David Hearn, Saul Rappaport, George Clark, and Ben Laufer. Credit: MIT Physics.
“George helped chart the future of X-ray astronomy by prioritizing the Chandra X-ray Observatory,” says MIT Kavli Institute director Robert Simcoe. “He played a major role in the discovery of celestial gamma-ray sources.”
On the MIT Physics faculty for 44 years, Clark recruited and mentored several generations of leading astrophysicists. George was a founding member of MIT’s Center for Space Research, now the MIT Kavli Institute.
Clark was a principal investigator on the Seventh Orbiting Solar Observatory, or OSO-7 Satellite, for MIT’s first X-ray satellite experiment which yielded, in collaboration with MIT research scientist Thomas Markert, an all-sky survey of X-ray sources.
Clark received the NASA Exceptional Scientific Achievement Award for his work as PI of the Einstein Observatory Focal Plane Crystal Spectrometer, which used the technique of Bragg spectroscopy to perform high-resolution spectroscopic studies of cosmic X-ray sources in the 0.2-3 keV energy range, on the Einstein X-Ray Observatory (HEAO-2, 1978-1981). The second of NASA’s three High Energy Astrophysical Observatories, Einstein was a Large Orbiting X-Ray Telescope (LOXT) — the first fully imaging X-ray telescope put into space.
As a member of the National Academy of Sciences decadal study (the “Field Report”) Clark helped chart the future of X-ray astronomy by prioritizing the development of Einstein’ssuccessor, the Advanced X-Ray Astrophysics Facility (AXAF), later renamed the Chandra X-ray Observatory. Chandra features a high-resolution large collecting area, and sensitivity to higher energy X-rays to study extremely faint sources in crowded fields. Clark used Chandra data to study the grain-scattered X-ray halos of accretion-powered binaries, and from the shape and size of a halo he tried to figure out the location and characteristics of the dust and the distance of the star.