The energy generated in the sun comes from an exothermic set of reactions, where the first one, pp fusion,

is governed by the weak interaction, which makes it the slowest reaction, and therefore it determines

the suns lifetime. However, its slow rate entails that a measurement of its cross-section is impossible.

Instead, the reactions cross-section must be calculated from theory.

In our theoretical work we are trying to resolve the pp fusion

by using a method named Effective Field Theory (EFT) and fixing the corresponding coupling constants from a parallel weak decay, namely triton beta decay. We are able to resolve the pp

fusion and to determine the sun's life time to unprecedented accuracy.