This prediction is based on computer models of the cluster, which describe the various paths the divided supernova light is taking through the maze of clumpy dark matter in the galactic grouping. Each image takes a different route through the cluster and arrives at a different time, due in part to differences in the length of the pathways the light follows to reach Earth. The four supernova images captured by Hubble, for example, appeared within a few days or weeks of each other.