Comets and solar neutrino puzzle

It is shown how a new class of chemically inhomogeneous solar models can be constructed which lead to a present-day sun possessing a small burnt-out core consisting of at least 95 percent of elements heavier than He. Such models with a core mass fraction of 1 percent have a neutrino flux of the order 2 SNU, in line with the observed value. It is shown how these models overcome some of the problems associated with the earlier inhomogeneous models of Prentice (1976). Since comets have a composition very similar to that found for the solar core, it is suggested that comets may have formed through gravitational fragmentation of the original cloud of CNO grains which may have sedimented to form the sun's core.