The two smallest known moons orbiting Pluto were officially christened by the International Astronomical Union on 2 July 2013. The moon earlier known as P4, which was discovered in the summer of 2011, has been named Kerberos, after the three-headed dog of Greek mythology.
The second one called P5, which was discovered in the summer of 2012, was named Styx, after the mythological river that separates the world of the living from the realm of the dead. The moons join Pluto's previously known moons Charon, Nix and Hydra.
International Astronomical Union is in charge of approving celestial names. Pluto's moons are all named for characters associated with the underworld of Greek and Roman mythology, according to the International Astronomical Union rules. The two names were selected based on the results of an unprecedented internet vote that was held during February 2013, with the ballot receiving almost 500000 votes, including 30000 write-in suggestions.
When: 2 July 2013.