Overview

• In April 2025, IXPE recorded a 9.1% X-ray polarization degree from IGR J17091-3624, well above theoretical predictions based on standard corona geometry.
• The findings, published in Monthly Notices of the Royal Astronomical Society, showcase IXPE’s polarimetric precision and establish a new benchmark for black hole studies.
• Researchers have developed two explanations—Compton scattering off an accretion-disc wind and a relativistic corona outflow at ~0.2c—that can reproduce the high polarization without requiring an edge-on view.
• Both scenarios remain provisional and will be tested through planned follow-up IXPE observations, coordinated multiwavelength campaigns, and enhanced theoretical modeling.
• At roughly 28,000 light-years away, IGR J17091-3624’s corona and inner disc are too small to image directly, making polarimetry one of the few tools for probing near-black-hole plasma structure.