Formerly known as P4 and P5, Pluto’s tiniest moons now have official names: Kerberos and Styx.
The names were among the top three selected by voters during a two-week polling period; they have just been approved by the International Astronomical Union’s official nomenclature committee.
Thus, from this day forward, the two tiniest of rocks orbiting the overgrown-snowball-formerly-known-as-a-planet will conjure the tales of a three-headed dog guarding the gates of the underworld (Kerberos), and the river that doomed souls must cross (Styx).
“I hope the public is going to be pleased with the decisions that were made,” said Mark Showalter, the SETI Institute scientist who discovered P4 in 2011 and P5 in 2012. “I don’t think anybody’s ever tried quite the scale of an Internet poll as we did.”
Normally, whoever discovers a new celestial body gets a crack at naming it. But Showalter and his colleagues decided to take a more populist approach: They offered the public a chance to christen the new moons.
For two weeks in February, anyone with a computer could vote for their favorite names, or suggest ideas of their own. The caveats: Names needed to represent characters bearing more than just a passing relation to Pluto, the Greek god of the underworld, and must not have already been bestowed upon a celestial solar system object.
Initially, there were 12 names on the ballot, including such minions of Hades as Eurydice, Alecto, and Persephone. After a few days, Showalter added eight more. By the time voting closed, more than 450,000 votes had been cast, and voters had written in with 30,000 other options (including Stephen and Colbert, Mickey and Minnie, Potato and Pota(h)to, and various siblings claimed to be underworldly).
Among those write-ins was Vulcan, the Roman god of fire and volcanic fury, and the first addition to the ballot. Suggested on February 12 in a tweet by the actor William Shatner, Vulcan quickly zoomed ahead of the competition, leading the final tally with more than 170,00 votes.
Showalter submitted Vulcan, and second-place Cerberus (99,432 votes) to the International Astronomical Union for approval.
But when mulling over the names, the IAU found there were already too many objects named after Vulcan – not including the fictional home world of Star Trek's Mr. Spock – and after much deliberation, ruled that Vulcan wouldn’t work.
"What? That's impossible! I'm going to lead a revolt," Shatner said, when Wired told him of the outcome. "Pluto is so big and cold that it deserved to have a hot little rock running around it, named Vulcan – for fire."
Cerberus, too, ran into trouble – it was also already in use, by an asteroid. Instead, Showalter and colleagues tried Kerberos, the Greek spelling. And in place of Vulcan, they submitted third-place Styx (87,858 votes), which in addition to being a river, is also the name of the goddess of unbreakable oaths.
The IAU approved both.
“It’s a disappointment of mine that Vulcan wasn’t approved by the IAU, but there were so many issues around it having to do with its prior use,” Showalter said, noting that "Vulcan" is the name of a hypothetical inner solar system planet, as well as a class of sun-grazing asteroids.
The decision doesn’t rule out the possibility of something named after Vulcan in the Pluto system, however.
When the New Horizons spacecraft flies near the five-mooned world in 2015, it’ll be busy snapping photos of Pluto and its largest satellite, Charon. The images should return incredibly detailed views of these far-off iceballs, pictures that will allow scientists – and the rest of us – to discern surface features like craters and mountains. Unlike orbiting bodies, these features aren’t subject to many nomenclature restrictions (which leads to such awesomeness as Mount Doom on Titan and various artists on Mercury).
Right now, New Horizons is still 6 astronomical units away from Pluto, and the planetary runt is still just a bright point of light. By April 2015, the spacecraft will be close enough to the distant, icy world that its onboard cameras should produce images exceeding the resolution of the best Hubble Space Telescope images.
Maybe, hiding somewhere in those pixels, is a kick-ass ice volcano that could only be called Vulcan, an erupting fountain of fury that wouldn’t be the same by any other name.