The Astrophysics of Stellar Clusters

Stellar clusters are common. Globular clusters contain some of the oldest stars, whilst the youngest stars are found in OB associations or in other clusters associated with recent star formation. Such crowded places are hostile environments: a large fraction of stars will collide or undergo close encounters. I will explain how stellar clusters are factories for producing exotic objects, including black holes and neutron-star binaries. I will also discuss how planetary systems similar to our own solar system are vulnerable to breakup due to close encounters by passing stars. Thus by studying stellar clusters we will learn more about the rarity of planetary systems similar to our own solar system.