Robert Berrington, Haldan Cohn, and Phyllis Lugger (Indiana University)

Clusters of galaxies are some of the largest collections of matter in the cosmos. Thus, they are important tracers of the large-scale structure of the universe. Not long ago, it was thought that they exist in a balanced, steady state. However, recent evidence shows that most clusters of galaxies may not be in a steady state, but are constantly changing. In some cases, clusters of galaxies may even be growing by consuming other clusters. Scientists use supercomputers to find out how clusters of galaxies structurally evolve to their present state. Computer simulations allow us to see how matter within these clusters interacts over billions of years and how these interactions affect the shape and dynamics of these clusters.

The N-Body simulation

This movie shows the results of an N-Body simulation, a technique to model and study the complex interplay of matter, gravity and tides. The galaxies and dark matter in a cluster of galaxies are represented by millions of virtual particles, or bodies. The particles are placed in a way that represents how matter might be distributed in a cluster of galaxies somewhere in the universe. Then, the computer calculates the effect of gravity on that matter as time passes. The result is a time-lapse movie simulating the history of the cluster. In this simulation, the cluster and its contents—galaxies and dark matter—are evolving. How they evolve will help astronomers determine if clusters of galaxies are mostly in a steady state, or if they are continually cannibalizing each other.

Gordon Myers