A Star Cluster in Motion
Star clusters are a swarm of complex motions. The stars that compose globular clusters and many open clusters all orbit the cluster center, occasionally interacting, gravitationally, with a close-passing star. The orbits of stars around the cluster are typically not as circular as the orbits of planets in our solar system . Cluster stars frequently fall more directly toward the center and many times trace out unusual and complex loops . The vast space inside a cluster results in stars colliding only rarely. The above computer animation , derived from a type of computer code called an N-body simulation , shows 100 identical stars in a time-lapse movie where hundreds of years pass in one second.