The Phoenix Cluster (SPT-CL J2344-4243) is a massive, type I galaxy cluster located at its namesake constellation, the southern constellation of Phoenix. It was initially detected in 2010 using the Sunyaev–Zel'dovich effect by the South Pole Telescope collaboration.
It is one of the most massive galaxy clusters known, with the mass on the order of 2×1015 M☉. Most of the mass of the Phoenix Cluster is in the form of dark matter and its intracluster medium. The vast stellar halo of the Phoenix Cluster central galaxy extends to over 1.1 million light years from the center, making it one of the largest galaxies known. It is 22 times the diameter of our galaxy, and its starburst activity suggests that the galaxy is still growing larger.
The Phoenix Cluster is also producing more X-rays than any other known massive cluster.
Distance: 5,700,000,000 ly
Mass: 3.02 to 5 x 1045 kg