Martin Charles Weisskopf

Martin C. Weisskopf, a pioneering physicist whose work helped shape modern x-ray astronomy, died on 2 May 2026. Martin built the first astrophysical x-ray polarimeters in the 1970s, made major contributions to the development of the Chandra X-ray Observatory as project scientist, and led the first satellite mission devoted to x-ray polarimetry, the Imaging X-ray Polarimetry Explorer (IXPE).

Born in Omaha, Nebraska, on 21 April 1942, Martin graduated from Oberlin College magna cum laude with honors in physics in 1964. On the advice of his uncle, physicist Victor Weisskopf, he entered Brandeis University, where he obtained new upper limits to the electric dipole moment of the electron and received his PhD in 1969.

Martin changed fields to x-ray astronomy when he joined Robert Novick’s group at Columbia University in 1969. At Columbia, Martin was involved in several sounding rocket missions and learned the lesson that scientists, having the strongest interest in the success of an experiment, need to be cognizant of all the activities of a mission and to adapt their experiments to be completed on schedule while still meeting the scientific requirements.

Martin’s most formative experience at Columbia was designing and supervising the construction of a novel graphite crystal x-ray polarimeter built to observe the Crab Nebula. The experiment was flown in 1971 and detected polarization at the 15 ± 5 percent level; this was the first detection of x-ray polarization from an astrophysical source and confirmed the synchrotron origin of the x rays from the nebula. Soon after, Martin built the crystal polarimeters that were flown on the OSO-8 satellite in 1975. The polarization of the Crab Nebula was confirmed at the 20σ level. Unfortunately, only upper limits were obtained for other bright x-ray sources. This convinced Martin of the need to build a more sensitive polarimeter and to fly it as a dedicated mission. This became a personal quest for the next 50 years.

In 1977, Martin joined NASA’s Marshall Space Flight Center (MSFC) as the project scientist for the Advanced X-ray Astrophysics Facility, later renamed the Chandra X-ray Observatory, a role he held for 45 years until his retirement in 2022. Martin established a new paradigm for NASA project scientists, in that the project science team provided end-to-end scientific participation integrated with all project participants—scientists, engineers, management, industry, and science institutions—in working together toward the common objective of building and operating the world’s greatest x-ray astrophysics facility.

His approach ensured the scientific integrity of the mission and has culminated in Chandra’s outstanding record of scientific and technical success that continues to this day. Martin also founded the X-ray Astronomy Group at MSFC, cultivating a remarkable group of experimentalists who developed medium-to-high resolution, full-shell x-ray optics that have flown in numerous astrophysics missions.

While working on Chandra, Martin proposed to NASA many x-ray polarimetry missions. In 2007, he joined efforts with three Italian colleagues, Enrico Costa, Ronaldo Bellazzini, and Paolo Soffitta, who had developed an x-ray polarimeter exploiting the photoelectric effect in a gas-filled detector. Combined with x-ray optics from the X-ray Astronomy Group at MSFC, this new technology enabled an order-of-magnitude leap in sensitivity. Reproposed in 2014 as IXPE, the mission was selected in 2017 and launched in 2021.

IXPE has provided a new tool for astrophysics research whose results are changing our current understanding of high-energy phenomena in the galaxy and the local universe. Thus, 50 years after his first rocket flight detecting polarized x rays from the Crab Nebula, a new window on the x-ray sky was opened with a dedicated mission under Martin’s leadership.

Martin received the Rossi Prize of the High Energy Astrophysics Division of the American Astronomical Society twice, once for Chandra with Harvey Tananbaum (director of the Chandra X-ray Center at the Smithsonian Astrophysical Observatory), and once for IXPE with Paolo Soffitta (the IXPE Italian PI) and the IXPE team. He received the Accademia dei Lincei’s International Antonio Feltrinelli Award for Physical, Mathematical and Natural Sciences with Enrico Costa and Ronaldo Bellazzini, presented by the president of Italy. He was a fellow of the American Physical Society and of the International Society for Optical Engineering (SPIE) and a Legacy Fellow of the American Astronomical Society.

Martin Weisskopf approached his work and his life with great intensity, conviction, and compassion. Martin’s advice to young scientists has always been to figure out how to make an impact, devise a plan you believe in, and then act on your plan and never give up.

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