Distinction between models of interstellar grains

Abstract

A critical study is made of the various grain models. It is shown that the radar-scattering curve can be used effectively in discriminating the various grain models. The theoretical extinction curve for the graphite-core-ice-mantle model is shown to reproduce the observed reddening curve in the interval 7.0 µ^-1≤λ^-1≤0.47µ^-1. On the basis of the existing observational material one can rule out pure iron and an Oort-van de Hulst size distribution of dirty-ice particles as models for interstellar grain. Graphite-core-ice-mantle models generally seem to satisfy all of the existing observations.