Perseus galaxy cluster, satellite image

Perseus galaxy cluster, satellite image. The Perseus cluster (Abell 426) is a cluster of galaxies in the constellation Perseus. A new study of the Perseus galaxy cluster and others using Chandra and XMM-Newton has revealed a mysterious X-ray signal in the data. The signal is also seen in over 70 other galaxy clusters using XMM-Newton. This unidentified X-ray emission line - a spike of intensity centred on about 3.56 kiloelectron volts - requires further investigation to confirm both the signal's existence and nature. One possibility is this signal is from the decay of sterile neutrinos, one proposed candidate to explain dark matter. Imaged by the ESA's (European Space Agency's) XMM-Newton space observatory. Photo by Chandra: NASA/CXC/SAO/E.Bulbul, et al.; XMM-Newton: ESA/SCIENCE PHOTO LIBRARY