Tuesday, 2 July 2013

The Plutonian Sky

So, the IAU has announced that P4 and P5, the two tiny recently discovered moons of Pluto, are to be named Kerberos and Styx, the result of a popular poll being vetted by their own people for adherence to its rules. They join Charon, Nyx and Hydra in this surprisingly busy little sub-planetary system.

The clear winner of the public vote was Vulcan. I am very pleased that they didn't go with that. As much as I like the name, and as much as I understand the support for it, in my view Vulcan, god of the hearth, should be used for a fiery place, either somewhere volcanic or something near the Sun. Officially, the suggestion of Vulcan and Romulus - championed by none other than William 'the Shat' Shatner - referred to the god that was nephew to Pluto, and to the legendary founder of Rome. In reality, of course, they were suggested because they are planets in Star Trek, and while that's not a bad reason for choosing a name, it's not going to sway the IAU.

There were two reasons given for dismissing Vulcan. One was that it has already been used in astronomy. True, but given that it was used for a hypothetical planet within Mercury's orbit, the existence of which has long been refuted, this hardly seems to matter. Yes, there is also a class of asteroids named after this hypothetical body, but they remain hypothetical as well. Until we find some vulcanoids, I don't see that as a reasonable complaint. On the other hand, I fully agree with the second argument, that Vulcan is not sufficiently associated with Pluto. Also, many of the biggest Trek fans dislike the idea of using Vulcan for a piddly little frozen moon, preferring it to go to a major body - an extrasolar planet, perhaps.

Cerberus and Styx came in second and third in the poll. My own suggestions were Cerberus and Dis Pater, the latter of which didn't make it into the final poll (although there were some excellent suggestions, including Sisyphus, Erebus, Tartarus and Persephone). Cerberus, of course, was the mythical three-headed hound that guarded the gates to the underworld, while Styx was the river upon which Charon ferried the souls of the dead. Cerberus has already been used for an asteroid, and while there are doubled up names in the solar system, the IAU tries to avoid that sort of things these days. They got round it by using the Greek spelling, Kerberos. How this works in Greece, where they generally use Greek names for the planets anyway, I don't know. Styx was, happily, free for use.

Mark Showalter, the discoverer of the moons with the New Horizons team, presented a fascinating live feed on the announcement, in which explained the process of the decision and suggested possible naming schemes for surface features of Pluto (the New Horizons spacecraft is expected to reach a close enough point to resolve surface features in around two years). The suggestions included using Disney and Star Trek characters for different types of terrain. As an aside, Showalter is one hell of an astronomer, having already discovered the Saturnian moon Pan, the Uranian moons Mab and Cupid and several tenuous planetary rings.

New Horizons will continue to send data back to NASA and there will doubtless be further discoveries to come. Could Pluto have more moons, or even a ring? Thankfully, there are plenty more potential names up for use. I just hope they keep Vulcan for something more fitting. It's only logical.

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