Imperturbable Corona: How Polarization Revealed the Black Hole's Stable Geometry
May 2022. The space polarimeter IXPE, the spectroscope NuSTAR, and the monitor NICER simultaneously stared at one spot in the sky — at the black hole in the Cygnus X-1 system, where it orbits a blue supergiant in a close binary system with a period of 5.6 days.