Formation of planetary systems: a simple synthetical approach

It is shown that by means of elementary assumptions it is possible to obtain models of planetary systems not too different from the observed case. Such assumptions are shown to be the bulk of more detailed models as those by Dole (1970) and Isaacman and Sagan (1977). An accurate fit with the features of the Solar System can be obtained only by ad hoc assumptions on various physical quantities and depends also on the possibility of taking into account stochastic processes in the numerical code. The authors discuss various cases and attempt to derive best fit values for the free parameters of the model. The hypothesis of a moderate mass depletion in the region of outer planets is strongly supported by the results. (Auth.)