The 'standard' Sun -: Modelling and helioseismology

The 'standard' solar model is based on a number of simplifying assumptions and depends on knowledge of the physical properties of matter in the Sun. Given these assumptions, the constraint that the model have the observed surface luminosity provides an estimate of the initial solar helium abundance. From helioseismic analyses further information can be obtained about the present composition, including a fairly precise measure of the envelope helium abundance and an estimate of the hydrogen profile in the radiative interior. It must be emphasized, however, that these inferences may suffer from systematic error arising from incomplete knowledge about the equation of state and opacity of the solar interior.