Limited solubility of iron in the Sun's interior

Abstract

STRIPPED iron nuclei in a hydrogen plasma under central solar conditions, according to the classical Debye–Hückel model, would undergo phase separation for concentrations well below the cosmic abundance value. The higher concentration corrections, needed to characterise the iron-rich phase, lead to enhanced solubility for a simplified model where the electrons form a uniform background. Support for an iron-rich phase coalescing in the solar interior requires more accurate treatment of bound and partially bound electrons in such a mixture. The results of the Debye–Hückel model where the electrons are treated discretely and as a continuum, are reported here and support the possibility of phase separation. The physical cause of that phase separation is simply that the potential energy is lower in the separated phases than in the mixture because the local charge neutralisation is much better satisfied in the two separated phases.