The talk is focused on the interplay between astrophysics and nuclear physics, which is called “nuclear astrophysics”. I give an introduction about the way Stars are born and how different Stars evolve. I show that nuclear reactions play a central role in the star evolution: they produce the energy released by the stars, and determine the nucleosynthesis of heavy elements.

I present the different stages of nucleosynthesis, starting from elements created after the Big-Bang, to the different reaction cycles occurring in the star evolution, and to explosive events such as Supernovae. I show that nuclear reactions relevant for astrophysics are difficult to study in the laboratory. However, recent technological progresses have provided us with many new data, in particular about reactions involving radioactive nuclei.