The Horologium-Reticulum Supercluster
This behemoth structure, containing more than 350,000 separate galaxies (30,000 large galaxies, 5,000 galaxy groups with more than 300,000 dwarf galaxies), is located about 700 million light-years from Earth. At least, the closest part of it is. This thing is literally so large, we aren’t entirely sure where the farthest end is, but it’s believed to be at least 1.2 billion light-years away from us — stretching across more than 550 million light-years in total.
Included in the Horologium-Reticulum Supercluster, is Abell 3266, one of the most massive regions in our local universe. Incidentally, a huge cloud of gas, stretching out more than 5 million light-years along, is quickly approaching the cluster, which will reignite an era of star formation for the galaxies that will be impacted.