Traveling waves in an evolving interstellar gas cloud

Abstract

This paper considers the possible emergence of traveling waves within an evolving interstellar gas cloud. To model this evolution, we use Euler–Poisson equations with the additional assumptions that the gas is incompressible, stratified, and self-gravitating. Within this framework, we establish that when the cloud has low density, the speed of these traveling waves is low. We suggest that the self-gravitational coalescence of embedded solid matter in the gas to form larger aggregates, such as cometary nuclei, may occur in the vicinity of wave crests where the mass density is highest. This idea is consistent with the widely agreed mechanism for planetary formation in proto-planetary disks, namely, that the accumulation of solids to form larger planetoids is initiated at the location of pressure maxima in the gas disk.