At the beginning of X-Ray Astronomy Vitali Ginzburg stated that polarimetry would play a major role as a diagnostic in this domain. Experiments of Polarimetry were trailing after a few years the progresses of the discipline. But when Giacconi performed the revolution of the optics, polarimetry, totally mismatched in sensitivity, was kept aside for almost 35 years.
The situation totally changed with the invention of detectors based on the photoelectric effect in gas. The Imaging X-Ray Polarimetry Explorer, based on this technique, allowed to extend to polarimetry the break-through in sensitivity performed with the Einstein Satellite.
Data from IXPE, by introducing two new observational parameters are challenging many established views in Relativistic Astrophysics.