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A Speculation into the Origin of Neutral Globules in Planetary Nebulae: Could the Helix’s Comets Really be Comets?

Published online by Cambridge University Press:  25 April 2016

Grant Gussie
Grant Gussie*
Affiliation:
Department of Physics, University of Tasmania, GPO Box 252C, Hobart, Tas. 7001, Australia. [email protected]
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Abstract

A novel explanation for the origin of the cometary globules within NGC 7293 (the ‘Helix’ planetary nebula) is examined, namely that these globules originate as massive cometary bodies at large astrocentric radii. The masses of such hypothetical cometary bodies would have to be several orders of magnitude larger than those of any such bodies observed in our solar system in order to supply the observed mass of neutral gas. It is, however, shown that comets at ‘outer Oort cloud’ distances are likely to survive past the red giant and asymptotic giant branch evolutionary phases of the central star, allowing them to survive until the formation of the planetary nebula. Some observational tests of this hypothesis are proposed.

Keywords

planetary nebulae — ISMmolecular — comets
Type
Galactic and Stellar
Information
Publications of the Astronomical Society of Australia , Volume 12 , Issue 2 , August 1995 , pp. 170 - 173
Copyright
Copyright © Astronomical Society of Australia 1995

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