The Origin of Comets

Abstract

The evolution of the solar system is surveyed, it being presumed that the Sun, Jupiter, and Saturn formed rather quickly and essentially with the composition of the original collapsing cloud of dust and gas. Just as the refractory material of the cloud is considered to have formed into planetesimals, from which the terrestrial planets collected, so is the icy material supposed to have produced comets, or cometesimals, from which Uranus and Neptune (and to some extent Saturn and Jupiter) were built up. The presence of a residual belt of comets beyond the orbit of Neptune is discussed, analysis of possible perturbative effects on P/Halley indicating that the total mass of such a belt at 50 AU from the Sun could not now exceed the mass of the Earth.