Astronomers have found the most distant galaxy cluster ever seen: the sexily-named SXDF-XCLJ0218-0510. First, the picture, then the words:
Yikes! What's all that then? Okay, first, this picture is littered with stars and galaxies. The galaxies are so far away they're hard to distinguish from the stars! The dots that have arrows pointing to them are the galaxies that are most likely part of the cluster. The ones with circles have had their distance measured and are known to be part of the cluster for sure. The contour lines represent the detection of very hot gas, which is a dead giveaway that we're dealing with a cluster here; all big clusters have gas swirling around them that gives off X-rays; the lines are like a topographic map telling you where the (otherwise invisible) gas is in the picture. "So what?", you might say. We've seen lots of clusters before. Ah, ...
