14 DAY TRIAL // Now that astronomers established the existence of a new moon around Pluto, they also have to name the object. Given the significance that names of the dwarf planet and its other three moons have, it stands to reason that the fourth will also have to be named in a similar fashion.
In Roman mythology, Pluto was the ruler of the underworld, and was also known as Hades among the Greeks. As such, the dwarf planet's largest moon is called Charon, which is the name for the boatman that transported dead souls across the Styx river, into Hades.
The two smaller moons are called Nix and Hydra, for the Greek goddess of darkness and night and the mythological nine-headed serpent that battled Heracles, respectively. As such, before the new moon – P4 – was found, all names in this planetary system were consistent.
According to data provided by the Hubble Space Telescope – which discovered the object – the moon is between 8 and 21 miles (13 and 34 kilometers) in diameter. It lies between the orbits of Nix and Hydra, and is the smallest natural satellite around the planet.
Astronomers are now considering a name for P4, one that would reflect the nature of the system, and would also keep consistent with the names of all the other moons. At this point, Cerberus is a leading candidate. This is the name of the three-headed dog that guarded the entrance to Hades.
The object is “called P4 for the time being. It'll get a name, but it's not up to NASA to decide on it,” explains NASA Headquarters public affairs officer Trent Perrotto. Establishing a name for moons, asteroids and planets is the task of the International Astronomical Union (IAU).
“Objects crossing or approaching the orbit of Neptune […] notably [Pluto and its moons], are given mythological names associated with the underworld,” IAU guidelines on naming space objects say.
“We have a lot of colorful names to choose from because all the moon names come from, essentially, the minions of Hades. One name that seems to come up most is Cerberus, the dog who guards the gates to hell,” says SETI Institute planetary astronomer Mark Showalter.
Showalter is credited with discovering P4, and the IAU will try to respect his suggestion of naming the moon Cerberus as much as possible. “Cerberus: How could you go wrong with a name like that?” the expert says.
“But, unfortunately, Cerberus is already the name of an asteroid. The IAU balks at the idea of using asteroid names, although it's not necessarily out of the question. Even then, Kerberos, is closer to the original Greek, would be OK even if Cerberus is not,” he adds.
“I don't want to say that's the name we've chosen. There are a lot of interesting names being discussed,” Showalter concludes, quoted by Space. Even so, naming P4 Cerberus would make sense, seeing how Hydra and the three-headed dog were related in mythology.