SHAPING PLANETARY-NEBULAE

Hydrodynamical calculations are becoming increasingly successful at understanding the shapes and kinematics of planetary nebulae (PNs). The most successful models are two-dimensional interacting stellar wind models for which the PN nucleus is assumed to originally expel much or most of its mass in an equatorial waistband. The physics of the ensuing evolution seems to be explained nicely by a combination of hydrodynamics coupled with time-dependent stellar ionization and energy loss through nebular radiation. Recent radiation gas dynamic calculations are shown to yield excellent agreement with data.