  We observe photons and neutrinos from stars. Based on these observations,
complemented by measurements of cosmic rays energies and composition, we have
been able to constrain several models for the Big Bang and for stellar
evolution. But that is not enough. We also need to help this effort with
laboratory experiments. We are still far from being able to reproduce stellar
environments in a terrestrial laboratory. But in many cases we can obtain
accurate nuclear reaction rates needed for modeling primordial nucleosynthesis
and hydrostatic burning in stars. The relevant reactions are difficult to
measure directly in the laboratory at the small astrophysical energies. In
recent years indirect reaction methods have been developed and applied to
extract low-energy astrophysical S-factors. These methods require a combination
of new experimental techniques and theoretical efforts, which are the subject
of this short review.
