Three-dimensional radiation hydrodynamics simulation of the
convective envelope and the atmosphere of a red supergiant (e.g. α Ori) have been performed, including ionization effects and realistic (grey) opacities. Only a handful of giant convection cells with lifetimes up to a few years are found in the envelope.
The stellar surface itself is covered with smaller short-lived cells
related to the well-known solar granulation but differing in many ways. Pressure fluctuations, acoustic waves, and shocks play an important role affecting the surface energy fluxes and accordingly the emitted intensity. The interaction with convection and waves generates observable large-scale high-contrast surface features.
The complexity of the surface structures in the numerical models
which will probably be even higher in nature calls for interferometric observations with high spatial and some temporal resolution. The comparison with the results of numerical simulations will allow to deduce information about the nature of the surface phenomena and fundamental stellar parameters.