Pre-stellar interstellar dust

Abstract

Before we can properly build a theory for the origin of the solar system we must know what interstellar gas and dust look like in the pre-stellar stage. In this paper we have concentrated on the dust. We arrive at a description of this pre-stellar dust on which the limiting criteria are developed out of evolution from average dust properties. We identify two populations of dust grains: large core-mantle grains and very small bare particles. The cores are presumed to be silicate of size ∼0.05 μm while the mantles consist of a size distribution of accreted thicknesses of C, N, O molecules and radicals which have been photoprocessed and an outer layer of molecules (mostly CO) and other species accreted in the later stages of cloud contraction. Most of the mantles must contain stored energy, some perhaps with enough to blow off the mantle if sufficiently disturbed. The maximum mean size of the core-mantle particles is ∼0.21 μm. The bare particles have not yet been positively identified but are ∼0.005 μm in size and outnumber the core-mantle particles by ∼3000–4000 while the remaining hydrogen in the cloud is ∼1012 times more abundant than the core-mantle grains. Physical arguments are presented to explain the narrow size distribution of these two types of particles.