The largest moon of Pluto, Charon, is 750 miles (1,200 kilometers) across and was discovered in 1978. Pluto and Charon are tidally locked to one another, with the same sides always facing one another as they orbit. Two moons, Nix and Hydra, were discovered in 2005, and their existence was confirmed in 2006. Two more were discovered in 2011 and 2012, respectively. Each of these four recently discovered moons is very small—at most 100 miles (160 kilometers) across.