Relative motions of fragments of the split comets.: I. A new approach

Abstract

A new approach is formulated for the study of motions of the split comets. It is based on the assumption that two fragments of a comet separate at a rate that is determined primarily by a slight difference between their effective solar attractions rather than by the impulse imparted on them at the time of splitting. The net dynamical effect is interpreted as due to differential nongravitational forces, which depend on the size, density, structure, composition, and spin rate of the fragments. Since at least at smaller distances from the Sun these forces vary inversely as roughly the square of heliocentric distance, their dynamical effect resembles that of radiation pressure, so that the formalism developed for the motion of a dust particle in a cometary tail is applicable in principle. The calculations show that this approach provides reasonably good to excellent fits of the observed separations for a great majority of the split comets, and that it fails only in the case of Comet 1957 VI. The correlation between the differential nongravitational forces and the endurance of the fragment is investigated in terms of the physical behavior of the fragments, with the emphasis on the short-lived objects. Some of the unusual phenomena accompanying the split comets are discussed, and comments are also offered on the sequence of splitting for comets with multiple nuclei and on the distribution of the points of splitting in space.