Studying Stellar Populations in Omega Centauri with Phylogenetics

Context. The nature and formation history of our Galaxy’s largest and most enigmatic stellar cluster, known as Omega Centauri (ω Cen) remains debated.Aims. Here, we offer a novel approach to disentangling the complex stellar populations within ω Cen based on phylogenetics methodologies from evolutionary biology.Methods. These include the Gaussian mixture model and neighbor-joining clustering algorithms applied to a set of chemical abundances of ω Cen stellar members. Instead of using the classical approach in astronomy of grouping them into separate populations, we focused on how the stars are related to each other.Results. We could identify stars that likely formed in globular clusters versus those originating from prolonged in-situ star formation and how these stars interconnect.Conclusions. Our analysis supports the hypothesis that ω Cen might be a nuclear star cluster of a galaxy accreted by the Milky Way with a mass of about 109 M⊙. Furthermore, we revealed the existence of a previously unidentified in-situ stellar population with a distinct chemical pattern unlike any known population found in the Milky Way to date. Our analysis of ω Cen is an example of the success of cross-disciplinary research and shows the vast potential of applying evolutionary biology tools to astronomical datasets, opening new avenues for understanding the chemical evolution of complex stellar systems. © The Authors 2025.