Dark matter ring formation. Computer graphic showing the formation of the dark matter ring detected in the galaxy cluster CI 0024+17 (see R980/230). The timeline covers the 2.5 billion years before now, starting at the top and ending with the current situation at the bottom. Cluster CI 0024+17 formed from the collision of two smaller galaxy clusters. The dark matter ring was detected by the Hubble Space Telescope, which used the gravitational lensing effects of the cluster to determine the distribution of mass within it. Massive areas without stars were deemed to contain dark matter, which does not emit or reflect light. Dark matter is thought to form much of the universe, and this ring is the best evidence yet for its existence.