Stability of chiral colloidal droplets*

We report experiments on a two-dimensional cohesive chiral fluid consisting of millions of spinning colloidal magnets suspended in water. Droplets made of this fluid are observed to swirl around and collapse into a single central superdroplet in a process reminiscent of the accretion of matter during the formation of a black hole. We put forth a minimal but complete hydrodynamic description of this active chiral fluid and use it to analyze the stability of the droplet states.