Shot in the dark

A cosmic collision between two galaxy clusters, known as the Bullet Cluster has provided researchers with evidences for the existence of dark matter. The forces involved in this event are so great that the X-ray emitting plasma is ripped away from the galaxy and any dark matter that might be present within them. The Bullet Cluster is valuable because the collision has separated the dominant baryonic component from the dominant dark matter. The scientists measured the shapes of very faint galaxies, taking care to only use those that were likely to be located behind the galaxy cluster and therefore lensed. A growing number of physicists have begun exploring methods to solve Zwicky's puzzle by developing alternative theories. Reserachers have analyzed that the strength of he Bullet Cluster lensing peaks compared with the total baryonic mass is similar to that of other clusters in which the stars and plasma are coincident.