The possibility of discovering more moons is part of the reason that the astronomers have not proposed a formal name for P4, let alone P5. "The reason that P4 doesn't have a name yet is we've been tracking possible P5s," Showalter says, adding that none had panned out before Saturday. "If you have two moons to name then it becomes kind of a different process than naming one."
By convention, the moons' names come out of Greek mythology, in this case from stories related to Pluto, the god of the underworld. But the specific choice of myth depends on how many names are needed—if P4 and P5 prove to be the last of the tiny, faint moons to be discovered, then a two-character tale will suffice. "For example, there's the story of Orpheus, the only mortal to go into the underworld and return to save his wife, Eurydice," Showalter says. "Maybe a good name for them would be Orpheus and Eurydice." But if astronomers discover another moon circling Pluto, it's a different story—and a different myth—altogether.