Evolution of protostars. I. Global formulation and results

We review the controversy and give a new formulation for the problem of the evolution of protostars. Our method entails the division of the global problem into a set of more manageable subproblems. We derive the jump conditions of the radiative accretion shock which joins the hydrostatic mass-gaining core to the dynamic inner cloud envelope. Different approximations hold with high accuracy in the regions that we call the dust envelope, the opacity gap, the radiative precusor, the accretion shock, and the hydrostatic core. In no region do we need to solve equations more complicated than ordinary differential equations. Thus, standard integration schemes yield the high accuracy needed to resolve complex spatial structures which span many orders of magnitude in density and temperature. Our 1 M/sub sun/ protostar ends its main accretion phase moderately high up in the H-R diagram. This star begins it pre--main-sequence phase of quasi-static contraction on a convective Hayashi track