How do the Milky Way’s tidal forces affect the outer edges of globular clusters?

The Milky Way’s tidal forces play a definitive role in shaping the structure of globular clusters. While these massive clusters are generally stable enough to resist total disruption by the galaxy, their outer dimensions are constrained by galactic tidal forces, particularly when they reach the closest points of their orbits to the galactic centre.1

In terms of stellar dynamics, these forces establish a "tidal radius," which serves as a cutoff point for star densities at the edge of the cluster. Consequently, the distribution of stars within a globular cluster is often modeled as an isothermal gas sphere that terminates at this tidal boundary. By defining this limit, the Milky Way’s gravity effectively dictates the physical extent of the cluster, marking the transition where the cluster's internal gravitational hold on its stars is overcome by the external influence of the galaxy.21