This image shows one of the newly discovered superclusters of galaxies, PLCK G214.6+37.0, detected by Planck and confirmed by XMM-Newton. This is the first supercluster to be discovered through its Sunyaev-Zel'dovich effect. The effect is the name for the cluster’s silhouette against the cosmic microwave background radiation. Combined with other observations, the Sunyaev-Zel'dovich effect allows astronomers to measure properties such as the temperature and density of the cluster’s hot gas where the galaxies are embedded.
The right panel shows the X-ray image of the supercluster obtained with XMM-Newton, which reveals that three galaxy clusters comprise this supercluster. The bright orange blob in the left panel shows the Sunyaev-Zel'dovich image of the supercluster, obtained by Planck. The X-ray contours are also superimposed on the Planck image.