RX-J2248 galaxy cluster

Beginning with today’s Photo of the Day, Fermilab Today will regularly feature snapshots taken with the Dark Energy Camera. This image shows the galaxy cluster RX-J2248, named for the ROSAT X-ray telescope, with which it was discovered. It has hundreds of old red galaxies as well as a massive amount of dark matter. View more of these snapshots and learn more about what you see at the Dark Energy Detectives website. Photo: Dark Energy Survey collaboration