Blazars polarization: what have we learned and what's next?

Since its launch, the Imaging X-ray Polarimetry Explorer (IXPE) has opened a new window onto blazars through the first systematic measurements of their X-ray polarization. IXPE observations reveal how polarization degree and angle evolve across blazar subclasses and flux states, providing direct constraints on magnetic-field geometry and the location of particle-acceleration sites. Time-resolved polarimetry has captured rapid angle rotations and polarization enhancements during flares, while coordinated multiwavelength campaigns have linked the X-ray–emitting region to optical, radio, and γ-ray behavior, testing synchrotron self-Compton versus external Compton scenarios.

Continued monitoring—together with theoretical investments and advancements—will further refine our understanding of blazar variability and solidify X-ray polarimetry as a key probe of jet physics in the coming decade.