Commission H4 Stellar Clusters

Scientific Objectives

It is widely accepted that stars do not form in isolation, but result from the fragmentation of molecular clouds, which leads to star cluster formation.  Star clusters are among the most important building blocks of galaxies and as such they are powerful tracers of the formation, assembly and evolutionary history of their parent galaxies. 

Star clusters are also the observational foundation for stellar astrophysics and evolution, provide essential tracers of galactic structure, and are unique stellar dynamical environments. Star formation, stellar structure, stellar evolution and stellar nucleosynthesis continue to benefit and improve tremendously from the study of these systems. Additionally, fundamental quantities such as the initial mass function can be successfully derived from studying star clusters.  Star cluster studies thus span the fields of Galactic and extragalactic astrophysics, while heavily affecting our detailed understanding of the process of star formation in dense environments.

The scientific objectives of Commission H4 include the following research into star clusters across all stellar mass ranges, whether or not gravitationally bound:

• Provide an operational definition of what is considered a “star cluster or association”;
• The study of gas and dust-embedded star clusters;
• The study of open clusters and stellar associations;
• The detailed study of individual stars in globular clusters in the Milky Way Galaxy;
• The study of old globular cluster populations in external galaxies;
• Starburst and nuclear star clusters;
• The transition between the most massive star clusters and the dwarf galaxy regime;

Observational, theoretical, and numerical studies reveal important information about star clusters including:

• The stellar populations (including binary populations, the initial mass function, exotic stellar types, interaction products, and elemental abundances);
• The kinematics and dynamics of star clusters and associations (e.g., initial conditions, ejecta and mergers);
• The formation, destruction, and cluster population properties (e.g., cluster mass and age distributions, luminosity functions etc);
• The integrated properties and their evolution;
• The environmental impact of stars clusters on their galaxies, in the near and far Universe.

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