CfA Colloquium Schedule Fall 2004
 4 November 2004

4 November 2004

Speaker: Bruce Balick (University of Washington)

Title: Stars as Artists: The Shaping of Planetary Nebulae

Abstract: Ten years of Hubble images of planetary nebulae have shown their astounding high-order symmetries in the mass that they eject once they start to ascend the AGB. These symmetries are too common, on the one hand, and complex, on the other, to provide any confidence that we presently understand how stars eject mass late in their lives. At the same time trends seen in the Hubble images, their changes with time, and maps of Doppler shifts represent a very nice set of constraints on any proposed mechanism for shaping mass loss. The goal of the talk is to present representative data, identify the interesting patterns that have emerged, and describe broad classes of new types of models which, at this point in the march of science, are guides to organizing our ignorance of how old stars evolve. The most hopeful of these requires the emergence of long-lived magnetic fields released from a spinning core dynamo by very deep convection near the end of the AGB ascent. MHD models are promising, but certainly not yet viable.

Video of the Presentation (Talks can be viewed with RealPlayer. Free download is available from )

References for students:

  1. The extraordinary deaths of ordinary stars, B. Balick and A. Frank, Scientific American, vol. 296, p26, July 2004
  2. Sowing the seeds of asymmetry, R. Sahai, in Asymmetrical Planetary Nebulae III, ASP Conference Series Vol 313, p141, 2004


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