The black hole Cygnus X-1 is one of the most studied in our galaxy. It pairs with a normal star, pulling matter from it. The gas spirals into a glowing disk, like water down a drain, and above the disk hangs a scorching corona — a cloud of electrons at temperatures of hundreds of millions of degrees. It is in this corona that X-ray photons gain extra energy and become polarized, meaning their oscillations align in one direction.

New observations from several space telescopes show that the corona is not stationary. It streams outward at about 0.3 times the speed of light — roughly 90,000 kilometers per second. This wind accelerates electrons, and they scatter light unevenly: photons moving against the wind gain more energy than those moving with it. This explains why the polarization barely changes with photon energy, even though it would normally be expected to rotate significantly.

Comparison with calculations shows that the black hole rotates slowly. If it spun fast, its gravity would cause the polarization plane to rotate by different angles for different energies. Observations show no such rotation. So the hole itself plays little role in creating polarization: it's all the work of its corona-wind.

Thus Cygnus X-1 again confirms: even in a quiescent state, a black hole is not asleep but continuously ejects matter. And this ejection can be seen not only in brightness but also in how light oscillates.