XMMXCS 2215-1738 is a galaxy cluster that lies 10 billion light-years away and has a redshift value of z=1.45.
The cluster was discovered and studied using the XMM-Newton and Keck Telescopes.
[1][3] Led by University of Sussex researchers, part of the XMM Cluster Survey (XCS) used X-ray Multi Mirror (XMM) Newton satellite to find it, Keck Telescope to determine distance, and used the Hubble Space Telescope to further image it.
It contains hundreds of reddish galaxies surrounded by x-ray-emitting gas.
[4] "The existence of the cluster so early in the history of the universe challenges ideas about how galaxies formed" The galaxy is called XMMXCS 2215-1734 in many references, with some news sources listing both names.