The adiabatic exponent in the solar core

We present helioseismic inversions of solar p-mode frequencies obtained by the Michelson Doppler Imager instrument of the Solar Oscillation Investigation project on board SOHO, which indicate a lower central value for the adiabatic exponent Gamma(1) in the Sun than in current models. We show how the inclusion of relativistic effects in the equation of state removes the discrepancy and allows almost perfect agreement in Gamma(1) between the models and the Sun. This increases our confidence both in the reliability of the equation-of-state calculation and the determination of solar p-mode frequencies.