Globular clusters reside in the galactic halo, a spherical region sparse in matter density, typically surrounding galaxies including our own Milky Way. They derive their name from their shape, as they are giant globes made of hundreds or thousands of stars orbiting each other. The cluster may contain up to millions of stars spanning up to 50 parsecs.
In the vast distances of inter-galactic space, globular clusters are like shining islands to travelers. While all three major starpowers maintain outposts in Milky Way globular clusters, some of them are still uncharted, and it is believed various outlaw groups and rogue regimes use them as their bases of operation.
Globular clusters contain some of the oldest stars in the universe crammed into a tight space only a few light-years across. Such tight quarters can provoke many close encounters of stellar bodies, some of which actually lead to partner swaps. If a neutron star with a companion, such as a white dwarf or a main sequence star, exchanges its partner with another neutron star, the resulting pair eventually will spiral together and collide explosively, creating a GRB.
The stars in globular clusters are sorted out according to their mass, governed by a gravitational ball game between stars. Heavier stars slow down and sink to the cluster's core, while lighter stars pick up speed and move across the cluster to its periphery. This process is called mass segregation.
For a list of globular clusters in the Milky Way halo, see List of Milky Way Globular Clusters. For a list of all known globular clusters in the universe, see Category:Globular clusters.