The Hubble Telescope has spotted a 5th moon for Pluto. So far, neither it nor moon 4 has names, they are just referred to as P4 and P5. Both are very small and seem to be related to the orbit of Pluto's largest moon, Charon. Pluto (which is smaller than the earth's moon) and Charon are similar to the earth in that they are considered more of a dual planet system than planet and orbiting moon. The two other moons of Pluto are Nix and Hydra. Read the full article on this discovery in the Scientific American.