Congratulations Pluto! We Earthlings have named two of your offspring Kerberos and Styx. You may have noticed that, in keeping with your Hellish roots, we’ve named your cute little bundles of rock after deities of the Underworld. What’s that? You’d rather one be named after a science fiction planet?! And Captain Kirk gave you his blessing?! Tough.

Yes, the day has come, Pluto’s two newly-discovered moons (originally designated “P4″ and “P5″) have been officially been named by the International Astronomical Union (IAU). And they took into consideration the Pluto Rocks! naming poll that was organized by the SETI Institute. But they didn’t exactly agree with the outright winner.

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“The IAU is pleased to announce that today it has officially recognized the names Kerberos and Styx for the fourth and fifth moons of Pluto respectively,” the IAU said in a statement Tuesday. “These names were backed by voters in a recently held popular contest, aimed at allowing the public to suggest names for the two recently discovered moons of the most famous dwarf planet in the Solar System.”

Kerberos was discovered in 2011 and Styx in 2012. The pair were uncovered by Hubble Space Telescope surveys of the volume of space surrounding the dwarf planet in support of the 2015 NASA New Horizons flyby. The search was led by SETI Institute astronomers. New Horizons is currently flying through interplanetary space a little under 5 Astronomical Units (AU) from Pluto, but since launch in 2006, astronomers have grown concerned about rocky debris that could surround Pluto. Should the spacecraft slam into a previously unnoticed cloud of debris during the flyby, the mission could be wiped out.

The discovery of two more moons, in addition to Pluto’s original trio (Charon, Nix and Hydra), indicates there could be more rocky satellites out there. Although concern was growing, after extensive observational efforts, the New Horizons team will keep the spacecraft on its planned trajectory that will see a Pluto flyby in a little over 2 years time (although an emergency “bail-out” trajectory can be used if the Pluto neighborhood is deemed too rough).

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The SETI Pluto moons naming poll was wildly successful, especially after William Shatner, a.k.a. Captain James T. Kirk, suggested one of the moons should be named “Vulcan” after his Star Trek second in command Spock’s homeworld.

Shatner’s celebrity threw the poll into the limelight, ensuring a win for “Vulcan.” Although arguments were made for the suitability of the name, it didn’t quite fit. The astronomical naming convention has seen all the bodies in the Plutonian system named after mythological Greek and Roman deities of the Underworld.

“I was overwhelmed by the public response to the naming campaign,” said Mark Showalter, Senior Research Scientist at the SETI Institute. Nearly 500,000 votes were cast and 30,000 write-ins for name suggestions were received.

Hades, god of the underworld, who was also known as “Plouton” (meaning “Rich One”), was Latinized by the Romans to, simply, Pluto. In a nice little tidbit of astronomical history, the ninth planetary body from the sun was given that name by 11-year old schoolgirl Venetia Burney shortly after the small world was discovered by Clyde Tombaugh at Lowell Observatory in 1930. The mythological name for the dark and cold world started a tradition that has seen Pluto’s biggest satellite named after Charon (the ferryman of Hades who carries souls of the dead across the rivers Styx and Acheron) and two smaller moons Nix (is the Greek goddess of the night) and Hydra (the many-headed serpent).

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“Vulcan” is the god of fire in Roman mythology, however — not exactly someone you’ll find hanging out in the Underworld. So the IAU chose the next two most popular names: Styx (river of the Underworld) and Kerberos (after Cerberos, the hound of Hades in Greek mythology, spelled differently to avoid confusion with the asteroid 1865 Cerberus).

Pluto now has five moons, all with officially approved IAU names: Charon, Nix, Hydra, Kerberos and Styx. Sorry Trekkies, the popular vote, Vulcan, didn’t make the cut… this time.

Image credit: This image, taken by NASA’s Hubble Space Telescope, shows five moons orbiting the distant, icy dwarf planet Pluto. Credit: NASA, ESA, and M. Showalter (SETI Institute)