The evolution of a system consisted of a great number of bodies gravitationally interacting and aggregating under collision is considered. The body motions take place in the gravitational field of a central massive body (the Sun or a planet). It is assumed that gravitational interaction between bodies occurs only under their binary close approach. It is also assumed that within the period from one close approach to another the bodies move in Keplerian orbits, the orbits of all bodies being circular at the initial time of the system evolution. Thus, the system under consideration represents a model of the protoplanetary cloud at a certain stage of its evolution. It is shown that in the course of protoplanetary cloud evolution the ring zones of rarefaction and condensation of the matter emerge. Development of the condensation zones leads to the formation of planets most of which gain direct rotation about their axes.The regularities observed in orbital spacing of the formed planets are similar to those of real planetary and satellite systems.Specifically, in the considered case an approximate agreement takes place between the law of planetary distances and that of geometric progress.