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
potentially intermediate-mass black holes which can grow into
supermassive black holes in galactic nuclei. I will also discuss how
planetary systems similar to our own solar system are vulnerable
within stellar clusters due to interactions with other stars.  Thus by
studying stellar clusters we will learn more about the rarity of
planetary systems similar to our own solar system. I will explain how
the depletion of red giants in the very centre of our own galaxy may
tell us something about its history.