According to a Cornell astrophysicist, a “beautiful effect” predicted by quantum electrodynamics (QED) could explain the perplexing initial observations of polarized X-rays emitted by a magnetar, a neutron star with a powerful magnetic field. Lower- and higher-energy X-rays were found to be polarized differently by NASA’s Imaging X-ray Polarimetry Explorer (IXPE) satellite last year, with electromagnetic fields oriented at right angles to one another, which was unexpected. Dong Lai, Ph.D. ’94, the Benson Jay Simon ’59, MBA ’62, and Mary Ellen Simon, M.A. ’63, Professor of Astrophysics in the College of Arts and Sciences, explained that this phenomenon can be explained naturally as a result of “photon metamorphosis,” which is a transformation of X-ray photons that has been theorized but never directly observed. Lai said that “In this observation of radiation from a faraway celestial object, we see a beautiful effect that is a manifestation of intricate, fundamental physics.”
The polarization observed in the magnetar’s X-rays can be thought of as two types of photons, with one flavor converting suddenly to the other under extreme conditions, explained Lai. This conversion is a natural consequence of the physics involved. While the observations of another magnetar with a stronger magnetic field did not show this polarization swing, Lai’s calculations suggest that the phenomenon would occur at deeper layers within the neutron star.
The study of X-rays from extreme cosmic objects such as neutron stars and black holes allows scientists to explore the behavior of matter in conditions that cannot be replicated in labs, and expands our knowledge of the diversity and beauty of the universe. Lai believes that the observations made by IXPE provide new insights into the surface environment of neutron stars.