Constraints on stellar interior physics from helioseismology

The richness and very high accuracy of the observed frequencies of solar oscillations provide tight constraints on the structure of the solar interior and hence on the assumptions underlying the calculation of solar models. This permits the use of the Sun as a laboratory for investigating the physics of stellar interiors. Important examples are the study of the equation of state in the convection zone, and the strong evidence for the importance of gravitational settling in the solar interior. On the other hand, the importance of studies of other stars is emphasized: for example, convective cores can only be investigated in more massive stars, and the large increase in computed opacities at temperatures below 10^6 K, convincingly confirmed by studies of double-mode Cepheids, has no effect on solar models.