Abell 2744, nicknamed Pandora's Cluster, is a giant galaxy cluster resulting from the simultaneous pile-up of at least four separate, smaller galaxy clusters that took place over a span of 350 million years. The galaxies in the cluster make up less than five percent of its mass. The gas (around 20 percent) is so hot that it shines only in X-rays. Dark matter makes up around 75 percent of the cluster's mass.

Images

image in the visible spectra -Hubble spacetelescope(Lars Holm Nielsen et al) retrieved 20/09/2011

video simulation of the merging events that created Abell 2744-Hubble spacetelescope(Lars Holm Nielsen et al) retrieved 20/09/2011