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Empirical data from Oort’s cloud

Published online by Cambridge University Press:  12 April 2016

A.H. Delsemme
A.H. Delsemme*
Affiliation:
Department of Physics and Astronomy, The University of Toledo, Toledo, OH 43606, USA

Abstract

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Empirical evidence about the size and the origin of the Oort’s cloud of comets is confronted with theories about its origin. The slow diffusion of the orbits of the “new” comets into the inner solar system implies a redefinition of the concept of “new” comet. A gradual transfer of orbital angular momentum occurs from the planets to the comets as the comets grow older on shorter period orbits. The observed retrograde to prograde ratio of the new comets is difficult to explain. Either it comes from a poorly understood observational bias, or from a neglected secular action of the Galaxy, or it implies a recent asymmetrical perturbation of the Oort’s cloud (less than 10−20 million years ago). The grazing incidence of a giant molecular cloud or an exceptionally close stellar passage would introduce such an asymmetry; this would also be true for the unseen hypothetical stellar companion of the Sun recently invoked to explain the periodicity of the geological extinction of species through violent cometary showers.

Type
Section II. The Oort Cloud of Comets
Information
International Astronomical Union Colloquium , Volume 83: Dynamics of Comets: Their Origin and Evolution , 1985 , pp. 71 - 85
Copyright
Copyright © Cambridge University Press 1985

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