Globular star clusters merging. Numerical simulation of the evolution and merging of two neighbouring globular clusters (red and blue). Globular star clusters are huge, old groups of hundreds of thousands of stars. They are thought to have formed very early in the life of the universe, contain few of the heavy elements that form planets, and exist in large spherical halos around many galaxies. Here, each cluster has 500 stars. The simulation follows the movements and gravitational interactions from random initial positions and velocities. Before the simulation starts, the camera view orbits the cluster to visualize the initial distribution. Subsequently, the mass segregation observed in real globular clusters appears. Low-mass stars are ejected from the globular cluster, while high-mass stars gravitate to the core of the globular cluster. At the same time, both globular clusters penetrate each other and combine to form a single globular cluster after two such transits.