July 2008 - Dark matter ring in galaxy cluster Cl 0024+17

This Hubble Space Telescope composite image shows a ghostly “ring” of dark matter in the galaxy cluster ZwCl0024+1652. The ring-like structure is evident in the blue map of the cluster’s dark matter distribution. The map is superimposed on a Hubble image of the cluster. The ring is one of the strongest pieces of evidence to date for the existence of dark matter, an unknown substance that pervades the Universe.