Origin of Amorphous Interstellar Grains

Abstract
Formation process of amorphous interstellar grains is studied theoretically. Crystallization in iron, magnesium silicate and carbon grains newly formed at various astrophysical sites is investigated. The probability of amorphous grain formation, which is determined by properties of matter and conditions of grain formation sites (pressure, cooling time scale and chemical composition), becomes larger with shorter cooling time and/or lower pressure. We expect that novae, supernovae and atmospheres of late type stars supply small amorphous grains of MgSiO3 or carbon.