Nebular Hydrodynamical Evolution

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Planetary nebulae (PN) are gaseous shells of varying shapes surrounding compact, hot central stars. They are formed by intense stellar winds from luminous, highly evolved red giant stars. This process of mass ejection robs the stars of their outer hydrogen- rich envelopes, leaving behind compact stars consisting predominantly of helium and heavier elements. Upon ejection of their hydrogen-rich envelopes and the initial formation of the PN, high-speed winds from the central stars shape the nebulae and affect their kinematic and thermodynamic properties. The Principal Investigators (PIs) propose to continue with their current NSF-funded study of the spatial and kinematic nature of PN. They will construct a two-dimensional hydrodynamic computer code, supplemented with collisional and photon heating and radiative cooling algorithms. The PIs plan to apply this code to shocks and collisional processes in the evolution of PN and their halos, the history of stellar winds, and the origin of the peculiar knots and rims of very low ionization embedded in some PN. Detailed comparisons with observational data of PN will be made.