The people have spoken. After a two-week voting period, the International Astronomical Union approved the names Kerberos and Styx as official replacements for P4 and P5 - monikers for Pluto's smallest moons.

Kerberos and Styx were discovered in 2011 and 2012, respectively, during observations of Pluto with the Hubble Space Telescope.

"Kerberos lies between the orbits of Nix and Hydra, two bigger moons discovered by Hubble in 2005, and Styx lies between Charon, the innermost and biggest moon, and Nix," the International Astronomical Union (IAU) said in a statement Tuesday.

Mark Showalter, the astronomer who discovered the moons and lead the naming campaign said he hoped the public is pleased with the new names of the moons. Voting was open for two weeks in February and more than 450,000 votes were cast amid some 30,000 potential moon names submitted by Showalter and the public.

The IAU acts as arbiter in the process when celestial bodies are given common names, ensuring the names work across different languages and cultures "in order to support collaborative worldwide research and avoid confusion."

To be consistent with the names of Pluto's other satellites, the names of the moons had to chosen from classical mythology with a particular reference to the underworld.

Vulcan, Cerberus and Styx were the top three contenders in the naming contest, but Vulcan was knocked out of the running despite leading the pack because it does not make a reference to the mythological underworld and because it has already been used to name a hypothetical planet between Mercury and the Sun. (While that planet does not exist, asteroids existing within Mercury's orbit are still referred to "vulcanoid.")

Cerberus is the multi-headed dog said to guard the entrance to the underworld and Styx is the goddess that ruled over the underworld river of the same name.

The spelling of Cerberus was changed to the Greek Kerberos to avoid confusion with an asteroid called 1865 Cerberus.