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 Γ₁ 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 Γ₁ 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.