P4 has been named Kerberos after the three-headed dog of Greek mythology and P5 has been named Styx, after the mythological river that separates the world of the living from the realm of the dead.
The names were chosen in keeping with the policy of naming moons in relation to the planet's name – is Pluto a planet again? The moons join Pluto's previously known moons Charon, Nix and Hydra, all characters associated with the Underworld of Greek and Roman mythology.
But SETI had conducted an online vote to choose the name and the hands down winner was Vulcan, as originally suggested by William Shatner.
The name was rejected because there is already something else named Vulcan and the character of Vulcan has very little to do with Pluto.
Shatner tweeted his responses:
I think they used us for promotional purposes! They're probably Star Wars fans!
Star Trek fans have had it rough. First JJ blows up Vulcan and now SETI finds a loophole to deny it from coming back!
Who'd ever thought I'd be betrayed by geeks and nerds? ;-)
The final comment at least suggests his outrage comes with tongue firmly planted in cheek.