In 2005 Hubble spotted two faint moons around Pluto, bringing the former planet's orbital partners up to three. Previously Pluto's only known moon had been Charon--the large body seen next to Pluto in the above image--which was discovered in 1978.
Dubbed Nix and Hydra, the two newer moons are about 5,000 times fainter than Pluto.
In a bit of a mixed blessing, Hubble also played a part in demoting Pluto to its current status as a dwarf planet (except in Illinois on March 13, 2009). Hubble pictures helped astronomers realize that one of Pluto's neighbors, Eris, is a larger body, kicking up a lively debate about what defines a planet.