Galaxy cluster MACS J0025.4-1222 collision. Combined Hubble Space Telescope (HST) and Chandra X-ray Observatory (CXO) image of a powerful collision of galaxy clusters. X-rays are pink, while visible light is blue and yellow. These observations indicate that a titanic collision has separated dark matter from ordinary matter in the MACS J0025.4-1222 cluster, an effect that has been detected previously in other clusters. This cluster is located in the constellation of Cetus and is billions of light years from Earth. The area seen here is 4.2 million light years across. This image was obtained in 2006, 2007 and 2008, using Hubble's WFPC2 and ACS instruments, and Chandra's ACIS instrument.