Abstract : 

The study of the long-dead early generations of massive stars is essential for building a comprehensive picture of the chemical evolution of the Universe and, ultimately, the origin of the elements. Although these stars can no longer be observed directly, their nature can be inferred indirectly by investigating low-mass, metal-poor stars in our Galaxy—some of which are nearly as old as the Universe itself. Among them, the peculiar, extremely iron-poor Carbon-Enhanced Metal-Poor (CEMP) stars stand out. Their precise origin remains debated, but they are thought to have formed from material enriched by only one, or at most a few, earlier massive stars. The main objective of this thesis is to explore the physics and nucleosynthesis of these early generations of massive stars. This is achieved by combining stellar evolution modeling, including the effects of rotation and full nucleosynthesis, with observations of CEMP stars.