Fractionated accretion and the solar neutrino problem

C. S. Jeffery, M. E. Bailey, and J. E. Chambers

During the course of its evolution, the Sun has accreted substantial quantities of material in the form of asteroids, comets, planetesimals and proto-planets. This debris is poor in hydrogen and helium and has substantially enriched the metallicity of the solar surface which must consequently be higher than that of the unobserved core. It is well known that compared with standard solar models a lower core metallicity results in a lower core temperature and a reduced flux of high-energy neutrinos. We estimate how much high-metallicity material could have been accreted during the solar lifetime, and how such accretion will affect the evolution of the Sun and other stars. We conclude that a few tens of Earth masses of fractionated material may have accreted onto the solar surface, and that this may provide a partial resolution of the solar neutrino problem. The solution may also explain the Faint Young Sun paradox and the inclination of the solar equator relative to the ecliptic.