Galaxy cluster RDCS 1252.9-2927, combined optical and X-ray image. The optical data shows the galaxies as bright spots, while the X-ray data shows a huge cloud of hot gas enveloping the cluster. An important finding was that this gas contains heavy elements from earlier generations of stars. The great distance of this cluster (9 billion light years away in the constellation Hydra), means we see it as it was in the early universe. The data shows that the cluster contains mature galaxies, despite being only 5 billion years old, supporting theories about the formation of galaxies and galaxy clusters. The results, from the Very Large Telescope and the Chandra X-ray observatory, were obtained in 2004 and published in 2005.