Simon Portegies Zwart (University of Amsterdam), Frank Summers (STScI)

Star clusters come in two general types: open clusters, which usually contain a few hundred stars at most, and globular clusters, which have many thousands of stars. How do star clusters change over time? This movie shows that the gravity that stars exert upon each other in a cluster cause them to dance, bob, and weave in beautiful and frenetic orbits. Indeed, the center of a globular cluster resembles a busy beehive, filled with dynamic activity.

The simulation

This visualization presents a globular cluster composed of 6,144 stars. The width of the frame represents more than a hundred trillion miles. As the movie unfolds, the evolution of the cluster is shown in this time-lapse movie, in which each second represents thousands of years passing by! As the stars orbit one other, several stars are ejected from the cluster through close gravitational encounters with more massive stars. The stars are shown in a scientific approximation of what the human eye would see: each star's brightness depends both on its intrinsic brightness and on its distance away from the virtual camera, while each star's color is only slightly exaggerated. These calculations were made with the GRAPE-4, one of the fastest special-purpose supercomputers in the world.

Charles Liu