Abstract

The history of the Universe can be revealed in the light of the stars, in particular in the oldest and the most pristine, also called metal-poor stars. From the chemical composition of these stars, it is possible to unveil the fossil fingerprint left from the previous generations of stars and open a window on the early Universe and the origins of the elements. Moreover, the kinematical properties of the most metal-poor stars are informative on the assembly of the Milky Way and the first structures in the Universe. In this seminar, I will focus on why/where to/how to investigate the most metal-poor stars. I will discuss some of the major achievements of one of the most efficient surveys that hunts for these old stars, the Pristine survey. Then, I will focus on a particular population of very metal-poor stars that surprisingly inhabit the Milky Way plane. I will discuss how this population is connected to the early formation and evolution of our Galaxy.