Statistical Dynamics and Accretion

Abstract

In Part I we discuss the velocity distribution of a cloud of non-interacting particles in the gravitational field of a point mass. It is assumed that at great distances the velocity-distribution is Maxwellian, and that the cloud and the point mass are in uniform relative motion. Values are obtained for the density, for the mean velocity, and for the components of velocity-dispersion at points on the axis of symmetry near the centre of attraction. These results are applied in Part II to the problem of accretion by stars of interstellar matter. It is found that, in the physical conditions usually assumed for interstellar matter, collisions between particles are relatively unimportant, and the rate of accretion is so extremely slow as to be negligible.