On the Mechanism of Accretion by Stars

The mechanism of accretion is investigated in detail for the case in which the interstellar material contains a sufficient proportion of molecules to ensure that the temperature is everywhere small. It is found that there is no unique steady-state solution and that the situation at any given time depends on the perturbations suffered by the system. The gravitational interaction between the interstellar material and the stars leads not only to an increase in the masses of the stars but also to a decrease in their peculiar velocities. The importance of these effects to stellar dynamics and to the evolution of the stars is briefly discussed.