The Hayashi Line
We have seen that convection can occur in quite different regions of a star. In this section we consider the limiting case of fully convective stars, i.e. stars which are convective in the whole interior from centre to photosphere, while only the atmosphere remains radiative. The Hayashi Line (HL) is defined as the locus in the Hertzsprung–Russell diagram of fully convective stars of given parameters (mass M and chemical composition).