Researchers utilizing NASA’s Imaging X-ray Polarimetry Explorer (IXPE) have potentially secured the first direct observation of vacuum birefringence, a concept in quantum electrodynamics first proposed in 1936. The findings, published in the journal Nature, center on observations of the magnetar 1E 1547-5408, a neutron star characterized by magnetic fields trillions of times more powerful than those produced by permanent magnets on Earth.
Between March and April 2025, the team conducted over 140 hours of coordinated observations using IXPE, NASA’s Neutron Star Interior Composition Explorer (NICER), and the CSIRO-operated Murriyang radio telescope in Australia. This effort marked the first time scientists performed simultaneous radio and X-ray polarization measurements on a magnetar.
The data revealed polarization levels nearly three times higher than those observed in comparable celestial sources. According to standard surface emission models, such high polarization was unexpected given the magnetar's magnetic field geometry. Scientists believe this discrepancy is explained by vacuum birefringence, a theory suggesting that extreme magnetic fields can alter the vacuum of space, causing it to act like a prism that filters and enhances light polarization.
"Our model suggests that reproducing the observed X-ray polarization signatures, while also satisfying the constraints set by radio observations, requires the presence of vacuum birefringence in the neutron star’s environment," stated Hoa Dinh Thi, a postdoctoral associate at Rice University and co-lead author of the study. Lead author Rachael Stewart, a Ph.D. candidate at George Washington University, noted that the findings provide insights into the fundamental nature of reality.
The IXPE mission, a collaboration between NASA and the Italian Space Agency, plans further observations to confirm these results and investigate other potential quantum electrodynamic effects. Source: NASA
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