Multiple Populations in Massive Clusters

Abstract

The first observations of light-element variations in massive clusters—commonly referred to as multiple populations—were made over 40 years ago. Despite significant advancements in spectroscopic and photometric data in recent years, which have provided highly detailed observational insights into multiple populations in clusters within the local universe, we still lack a comprehensive quantitative framework to fully explain the origin of these chemical peculiarities.

In this review, I briefly summarize the observational evidence gathered on multiple populations, their characteristics, and their trends with cluster parameters. Additionally, I highlight recent findings—both observational and theoretical—that hold great promise for understanding the origin of multiple populations and, ultimately, the processes driving star formation in massive clusters.