Abstract

Globular clusters (GCs) are old, collisional systems so the stars inside them interact on short timescales and have had a very long time in which to do so. These many and frequent interactions significantly affect both the structural and kinematic properties of GCs, so by studying their structure and kinematics we can learn about their evolution.

Some effects manifest as anisotropy in the velocity distributions, which require at least two (but preferably three) components of velocity information, and can only be seen with proper motion data. The Hubble Space Telescope and Gaia are highly complementary: HST has the depth to provide kinematics for a wide range of stellar masses, while Gaia has the spatial coverage to study changes across the whole cluster all the way out to its edges.

In my talk, I will focus on what we are learning about GCs from analysis of their kinematics using existing data, particularly proper motions from HST and Gaia. I will also discuss the advances that current and future telescopes will enable.