The Event Horizon Telescope looks at M87* and sees more than just a ring of light around a dark void. That light is twisted, like a corkscrew. The wavefront carries a helical structure that physicists call orbital angular momentum. Previously overlooked, it is now becoming a tool: the twist of light can reveal properties of the black hole itself.

A black hole acts like an optical q-plate. This element converts light polarization into a twist of the beam. The rotating and charged Kerr-Newman spacetime does the same to the radiation from the accretion disk. The formula for the average orbital momentum generalizes to include electric charge. The measured value for M87* is known to within about 3%. If the charge correction must not exceed this uncertainty, you get an inequality.

The result is an upper limit of Q/M ≲ 0.39. This is stricter than the previous limit of 0.90, which came from the shadow size. The method currently relies on a linear approximation in spin and an idealized q-plate model, but the orbital momentum is an observable quantity, extracted from data using phase retrieval techniques. This is not a model-dependent inference but a direct measurement.

Orbital angular momentum opens a new observational axis. Instead of the silhouette's geometry, one analyzes the phase structure of the radiation. This allows breaking degeneracies between charge, spin, and modifications of gravity. Numerical simulations of light propagation in a realistic accretion disk geometry will refine the connection between twist and black hole parameters. The method can be extended to scalar charges and non-singular solutions.

The twisted light from M87* is not just a pretty detail. It is a new channel of information about strong gravity. If confirmed by calculations, it will provide an independent check of shadow constraints and help search for deviations from Kerr solutions. The no-hair theorem says a black hole is described only by mass, spin, and charge. Now we have a way to test whether it really has no hair.