Observational properties of the open cluster system of the Milky Way and what they tell us about our Galaxy

TL;DR

This paper reviews the observational properties of the Milky Way's open cluster system, highlighting recent data advances and their implications for understanding the Galaxy's structure, evolution, and star formation.

Contribution

It provides a comprehensive overview of recent observational data and discusses their significance for Galactic structure, dynamics, and evolution studies.

Findings

Open cluster data enhances understanding of Galactic spiral structure.

Recent surveys improve insights into the Galaxy's chemical evolution.

Time-resolved data reveals dynamic processes in star formation.

Abstract

Almost 80 years have passed since Trumpler's analysis of the Galactic open cluster system laid one of the main foundations for understanding the nature and structure of the Milky Way. Since then, the open cluster system has been recognised as a key source of information for addressing a wide range of questions about the structure and evolution of our Galaxy. Over the last decade, surveys and individual observations from the ground and space have led to an explosion of astrometric, kinematic and multiwavelength photometric and spectroscopic open cluster data. In addition, a growing fraction of these data is often time-resolved. Together with increasing computing power and developments in classification techniques, the open cluster system reveals an increasingly clearer and more complete picture of our Galaxy. In this contribution, I review the observational properties of the Milky Way's open cluster system. I discuss what they can and cannot teach us now and in the near future about several topics such as the Galaxy's spiral structure and dynamics, chemical evolution, large-scale star formation, stellar populations and more.