Henric Krawczynski, the Wilfred R. and Ann Lee Konneker Distinguished Professor in Physics and chair of the department, has won the 2026 Bruno Rossi Prize, the most prestigious prize from the High Energy Astrophysics division of the American Astronomical Society. The prize was awarded for Krawczynski’s “pioneering contributions to the theory, instrumentation, and scientific interpretation of X-ray polarimetry,” according to the prize announcement.
X-rays are photons or particles of light carrying energy, momentum, and electric and magnetic fields. These fields can accelerate or decelerate electrically charged particles such as negatively charged electrons or positively charged atomic nuclei, both of which make up most of the matter that surrounds us.
X-rays emitted near highly magnetized neutron stars or reflecting off matter orbiting a black hole can become highly polarized, which means that their electric and magnetic fields point in certain directions. X-ray polarimeters can access this information that was hidden from previous generations of telescopes. The polarization encodes information on how the X-rays were emitted, and if and where they scattered before escaping the extreme environments that produce them.
Krawczynski’s theoretical work explored the degree of polarization of the X-rays from matter falling into black holes that were used to interpret the new data, as well as new statistical methods to analyze the polarimetry data.
The Society cited Krawczynski’s ongoing work as the principal investigator of XL-Calibur, a 12-meter-long X-ray telescope built and operated by an international collaboration of 50 scientists from Sweden, Japan, and the United States. XL-Calibur was flown on a stratospheric balloon flight from Sweden to Canada in July 2024. The flight allowed Krawczynski’s team to measure the polarization of the hard (particularly energetic) X-rays from the Crab supernova remnant and from the black hole Cygnus X-1 with unprecedented accuracy. That project enabled measurements that “revolutionized our understanding of black hole accretion and relativistic outflows,” the Society noted.
Krawczynski is also a member of the scientific team behind IXPE, a project that measures X-ray polarization from a space-based observatory. The IXPE team shared the Bruno Rossi Prize in 2024.
“Analyzing the data from IXPE and XL-Calibur was the highlight of my career so far,” said Krawczynski, a fellow of the McDonnell Center for the Space Sciences. “It was incredibly gratifying to suddenly get qualitatively new information about the most enigmatic objects in the universe.”
“The observational results were enabled by the work of more than 200 scientists, engineers, and technicians of the IXPE and XL-Calibur teams,” Krawczynski added. “I am humbled to receive this prize, and I hope I will be able to live up to it.”
