Galaxy cluster Abell 2218

In this image of galaxy cluster Abell 2218, the light from objects behind the cluster is spread in arc-like patterns by the cluster's gravitational field. This is similar to what happens when light passes through a glass ball. However, the mass needed to produce this distortion is much greater than the mass we can actually see. Images like these confirm the existence of dark matter.

W.Couch, University of New South Wales R. Ellis, Cambridge University

© NASA/STScI


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