What have we learnt about the Sun from the measurement of the 8B neutrino flux?

By combining the results of SNO and Super-Kamiokande one can derive—in the absence of sterile neutrinos—the total neutrino flux produced from 8B decay in the Sun. We use this information to check the accuracy of several input parameters of solar model calculations. Opacity and p–p fusion cross section are constrained by the 8B flux measurement to the level of few per cent. The central solar temperature is determined to the one-percent level. We also find an upper limit for the flux on Earth of sterile neutrinos. We discuss the role of nuclear physics uncertainties on these determinations.