2018ApJ...863..179S

The aim of Galactic archaeology is to recover the history of our Galaxy through the information encoded in stars. An unprobed assumption of this field is that the chemical composition of a star is an immutable marker of the gas from which it formed. It is vital to test this assumption on open clusters, a group of stars formed from the same gas. Previous investigations have shown that unevolved stars in clusters are chemically homogeneous within the typical uncertainties of these analyses, i.e., 15% of the elemental abundances. Our strictly differential analysis on five members of the Pleiades allows us to reach precisions of 5% for most elements and to unveil chemical anomalies within the cluster that could be explained by planet engulfment events. These results reveal that the evolution of planetary systems may alter the chemical composition of stars, challenging our capability of tagging them to their native environments, and also paving the way for the study of planetary architectures and their evolution, through the chemical pattern of their host stars.