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2. A Comparison of the Composition of New and Evolved Comets

Published online by Cambridge University Press:  12 April 2016

B. Donn

Abstract

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The intensity ratio of the continuum to the molecular emissions was estimated in the spectra of eight-five comets. These consisted of 34 new, 1/a (orig) < 100 x 10-6 AU-1, 31 more evolved with 102 < 1/a < 104, and 20 periodic comets, P < 103 years. In each age group the comets were divided into two distance intervals, the first observed at less than 1 AU from the sun and the second category observed at more than 1 AU. No significant difference among the patterns of relative intensity distribution among four age groups was found. No general evidence for a difference between pre- and post-perihelion observations was found although in a few cases a pronounced effect occurs. Four conclusions are drawn. (1) There is no readily apparent difference in continuum to emission intensity ratio between new and more evolved comets. (2) An intrinsic distribution of this characteristic does occur. (3) Periodic comets with weak continua derived from new comets with the same property. (4) No weakening of the continuum in general occurs following perihelion passage. The infrared evidence for Comet Encke suggests that the faintness of its continuum may be caused by a size distribution containing only particles larger than about 10 μm.

Type
Part I. Physical Nature of Comets
Information
International Astronomical Union Colloquium , Volume 39: Comets, Asteroids, Meteorites: Interrelations, Evolution and Origins , December 1977 , pp. 15 - 23
Copyright
Copyright © A.H. Delsemme 1977

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