Shao-Jun Zhang

A black hole with a magnetic field resembles a whirlpool in a river, where water doesn't flow into the vortex but swirls in place. Usually, the hole's rotation picks up waves and amplifies them: this is called superradiance. But add a magnetic field, and everything changes.

A black hole with an electric charge is like a vacuum cleaner that not only sucks in everything around it but can also hold light particles in orbit. These particles form a kind of fuzzy cloud around the hole — physicists call it a quasi-bound state.