Abell S1063, a galaxy cluster, was observed by the NASA/ESA Hubble Space Telescope as part of the Frontier Fields programme. The huge mass of the cluster — containing both baryonic matter and dark matter — acts as cosmic magnification glass and deforms objects behind it. In the past astronomers used this gravitational lensing effect to calculate the distribution of dark matter in galaxy clusters. Credit: NASA, ESA, and M. Montes (University of New South Wales, Sydney, Australia).
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