The equation of state for the solar interior

Helioseismology has become a very successful diagnosis of the equation of state. Although the gas in the solar interior is only weakly coupled and weakly degenerate, the great observational accuracy of the helioseismological measurements puts strong constraints on the nonideal part of the equation of state. For solar and stellar modelling, a high-quality equation of state is crucial. But the inverse is also true: the astrophysical data (helioseismic today, asteroseismic tomorrow) can put constraints on the physical formalisms, thus making the Sun and the stars laboratories for plasma physics.