In the last decade, the renewed interest toward very low-metallicity stars ([Fe/H]<-2) has culminated in a large number of spectroscopic and photometric surveys scanning extensive area of the sky in the attempt of finding these stars.
These very rare objects are key ingredients for the understanding of the formation of the Milky Way, offering a unique perspective into the earliest phases of our infant Galaxy.
Furthermore, in the last years, the advent of Gaia DR2, coupled with the outstanding improvements of the numerical techniques, led to the discovery of the debris of, at least, two major accretion events.
We are now beginning to unveil the complexity of our Galaxy.
In this project, we combine the study of a large sample of very low-metallicity stars with the look for accreted stars, to gain an unprecedented view into the early life of the Milky Way.
More info: Cordoni et al. (2020c)