The origin of planetary systems in the scenario of star formation

Theoretical models of the formation of the solar system are examined critically in a review focusing on the problems of specific angular momentum (j) and mass depletion. The values of j for the present solar system, a low-mass binary system, a twin binary, and a typical interstellar cloud are estimated as 1, 120, 170, and 10 to the 6th, respectively, and hypotheses advanced to explain the j gap between the solar system and its possible precursors are considered. Two general types of disk models are identified, one which assumes that the primeval solar nebula had mass 0.01-0.1 solar mass and experienced some mass depletion (e.g., Safronov, 1969) and one which assumes a very large nebula of 1 solar mass and strong mass depletion (e.g., Cameron, 1978). It is concluded that the uncertainties in both types of models make a choice between them impossible at present, but that the unresolved problems of the low-mass models appear less critical