Vacuum birefringence and the polarized X-ray emission from a radio magnetar

Nature, Published online: 05 August 2026; doi:10.1038/s41586-026-10859-z

Polarization measurements of the magnetar 1E 1547.0−5408 provide strong evidence that vacuum birefringence shapes X-ray propagation, offering an important observational test of quantum electrodynamics in extreme magnetic fields.