This color composite image of the galaxy cluster RDCS 1252.9-2927 shows the X-ray (purple) light from 70-million-degree Celsius gas in the cluster, and the optical (red, yellow and green) light from the galaxies in the cluster. The X-ray data was taken by the Chandra X-ray Observatory, and the optical data is from European Southern Observatory's Very Large Telescope (VLT) in Chile. X-ray data indicate that this cluster formed more than 8 billion years ago and has a mass at least 200 trillion times that of the Sun. It is the most massive cluster ever observed at such an early stage in the evolution of the universe. The width of the image spans 2 arcminutes.