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2026 Bruno Rossi Prize
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TOP HIGH-ENERGY PRIZE AWARDED TO HENRIC KRAWCZYNSKI FOR X-RAY POLARIMETRY
The 2026 Rossi Prize has been awarded to Henric Krawczynski of Washington University in St. Louis, for his contributions to the theory, instrumentation, and scientific interpretation of X-ray polarimetry.
Polarimetry measures not only the time and direction of arrival and energy of X-rays but also their polarization – the preferred direction in which the electric fields of the X-rays vibrate. Measuring the polarization of X-rays from black holes or neutron stars gives astronomers additional information about the origin of the X-rays, and the processes that affect the X-rays between their emission and their escape from the extreme black hole and neutron star environments.
As stellar mass black holes and neutron stars are thousands of light years away from us and are extremely compact (some 15 miles across), current technology does not allow us to image them. X-ray polarization is the next best diagnostic to infer the geometry of the hot X-ray bright regions surrounding these objects. Krawczynski’s work has included the first “hard” (higher-energy) X-ray polarization measurements with XL-Calibur, a balloon-borne X-ray telescope that flew in July 2024.
He has also been involved in important discoveries with NASA’s Imaging X-ray Polarimetry Explorer (IXPE). Through this, he has contributed to the understanding of how material from a companion star falls towards a black hole and configures itself under the influence of gravity and magnetic fields and becomes a bright source of X-rays.
“It is quite astonishing that elementary particles, X-rays, lock away information about their origin close to the most extreme objects in the Universe, black holes and neutron stars, and carry it over thousands of light years straight to us,” said Krawczynski, the Wilfred R. and Ann Lee Konneker Distinguished Professor of Physics in Arts & Sciences at Washington University.
“This is a great time for astrophysics, as we can use space telescopes to gather ever more precise and more detailed information about the properties of black holes and neutron stars, and employ supercomputers to recreate and understand the processes at work in these objects,” he continued.
The AAS High Energy Astrophysics Division (HEAD) awards the Rossi Prize in recognition of significant contributions as well as recent and original work in high-energy astrophysics. The prize is in honor of Professor Bruno Rossi, an authority on cosmic ray physics and a pioneer in the field of X-ray astronomy. The prize also includes an engraved certificate and a $1,500 award. Prof. Krawczynski will give a lecture at the 249th AAS meeting in Salt Lake City, Utah in January 2027.