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Evolution of PN Morphologies: Concepts, Models and Observations

Published online by Cambridge University Press:  07 August 2017

Bruce Balick*
Affiliation:
Astronomy Department, FM-20, University of Washington, Seattle WA 98195, U.S.A.

Abstract

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The shapes of planetary nebulae (PNs) provide paleontological clues about the origin and evolution of the gas expelled in the late phases of stellar evolution. The morphological classes of planetaries and various structural components of the nebulae are interpreted as hydrodynamic interactions of episodes of relatively brief, axisymmetric wind driven mass-loss events. Theoretical studies of the past five years are compared with extant data to show that astrophysical hydro models are achieving a very high level of success as explanations for the shapes of most PNs.

The most successful models are those for which the star is assumed to expel much or most of its mass in an equatorial wasteband. In stark contrast are dense ansae, dense and low-ionization knots of fast-moving gas, for which the mass distribution is decidedly polar. The origins of both the equatorial wastebands and polar knots remain decidedly enigmatic.

Information

Type
III. Highlights on the Nebulae
Copyright
Copyright © Kluwer 1993