A new model for cometary nuclei.

Abstract

A new model for the nucleus of comets is presented, hypothesizing formation at large heliocentric distances from many independent solid bodies. It is shown that such a configuration would collapse to a single assemblage if it is to survive into the inner solar system. Prior to collapse, the bodies would be subject to coating by interstellar gas and particles, which would form the material lost into the coma at subsequent inner solar system perihelia. Quantitative estimates place an upper limit to the body sizes of 2.3 m and a lower limit of the number as 3 x 10 to the 10th power with sizes of a few tenths of a micron and numbers of about 10 to the 33rd power most probable. The major structural and evolutionary features of such comet nuclei are consistent with the Whipple icy-conglomerate model.