... ESO . ... Galaxy Clusters . ... This image combines visible light exposures of galaxy cluster Abell 2744 taken by the NASA/ESA Hubble Space Telescope and the European Southern ObservatoryтАЩs Very Large Telescope, with X-ray data from NASAтАЩs Chandra X-ray Observatory and a mathematical reconstruction of the location of dark matter. ... Since dark matter makes up the lionтАЩs share of mass in the cluster тАФ around 75% тАФ this blue overlay reveals the location of the otherwise invisible dark...