Nuclear reactions for astrophysics studied at LUNA and in the Dresden Felsenkeller

Nuclear reactions power our Sun, and they create the chemical ele- ments that are necessary for human life. In order to correctly under- stand what happens in stars, one needs astronomical observations, but also nuclear physics data. For a number of astrophysical scenarios such as the Big Bang and our Sun, precise astronomical data are now avail-able. This calls for new nuclear reaction data of similar precision.
The nuclear reactions that are important for hydrogen burning in the Sun and for Big Bang nucleosynthesis have to be studied by low- energy experiments with intensive beams of stable ions. Due to the low cross sections involved, the experiments are usually performed in a low-background environment, such as an underground laboratory. The results obtained in the last decade at the pioneering LUNA 0.4 MV accelerator deep underground in the Gran Sasso laboratory, Italy, will be summarized, as well as related studies at surface-based ion accelerators.
New, higher-energy underground accelerators are necessary to ex- tend the energy range of the solar fusion data, and to address stellar helium and carbon burning. Relevant projects are underway both at LUNA and at the Dresden Felsenkeller.