Measurement of the {sup 3}He({sup 3}He,2p){sup 4}He Cross Section Down to the Lower Edge of the Solar Gamow Peak

The LUNA Collaboration has provided the first cross section measurements of the key reaction {sup 3}He({sup 3}He,2p){sup 4}He of the proton-proton chain at the thermal energy of the Sun. This successful project has shown that, by going underground and by using the typical techniques of the low background physics, it is possible to measure down to the energy of the nucleosynthesis inside the stars.