George Clark, professor emeritus and X-ray astronomy leader, dies at 94

Longtime MIT faculty member led investigations into cosmic-ray physics and gamma-ray and X-ray astronomy. MIT Emeritus George Whipple Clark PhD '52, an astrophysicist who was highly influential in X-ray and gamma-ray astronomy, died on April 6 in Boston. He was 94. Clark employed buckets, balloons, rockets, and satellites in his nearly lifelong pursuit to understand the nature and origins of cosmic rays, gamma rays, and X-rays. Clark discovered the polarization of cosmic-ray muons, collaborated with the late physics professor Bruno Rossi on several large ground-based cosmic-ray air shower experiments, and used balloon-borne and satellite instrumentation to locate X-ray sources. He was a principal scientist for satellite experiments that resulted in the discovery of high-energy gamma rays from the Milky Way galaxy, and produced evidence for an isotropic component that is now known to arise from other, more distant galaxies. His influential work in the use of balloon-borne instrumentation for observing celestial X-ray sources led to his discovery of high-energy X-rays from the Crab Nebula.