Circumstellar ring formation in rapidly rotating protostars

A three-dimensional hydrodynamic computer program is used to study rapidly rotating, self-gravitating polytropes with polytropic indices n = 0.8 and n = 1.8. The initial ratio of the rotational to gravitational potential energy is βi = 0.310 in both models. Both models, initially axisymmetric, are dynamically unstable toward the development of a nonaxisymmetric, two-armed spiral structure. Here the models are shown as they evolve to extremely nonlinear amplitudes: the end result in both cases is a type of fission. The models shed a fraction of their mass and angular momentum, producing a ring which surrounds a more centrally condensed object with βd= 0.27. The central object is a triaxial figure that is rotating about its shortest axis. The low-mass, roughly axisymmetric ring probably is capable of condensing into planets.