The names have now been chosen for the two most recently discovered moons of Pluto, it was announced last Tuesday by the The International Astronomical Union (IAU). The fourth and fifth known tiny moons are now known as Kerberos and Styx.
The names were chosen from those submitted in a public contest. Kerberos (the Greek spelling of Cerberus) was the many-headed dog which guarded the entrance to the underworld in Greek mythology and Styx was the goddess who ruled over the Styx river in the underworld.
It had been hoped by some people that Vulcan, well-known from Star Trek, would be chosen for one of the moons, but the IAU decided against it as the name doesn’t fit into the underworld mythology scheme. Just as well perhaps, since Vulcan was a planet, not a moon, anyway.
Both moons are really tiny in size, Kerberos being about 13-34 kilometres (8-21 miles) in diametre, and Styx about 10-25 kilometres (6-15 miles) in diametre.
The newly named moons join Hydra, Nix and Charon, the other three known moons of Pluto. It used to be thought unlikely that tiny Pluto had any moons at all. It’s still possible that others wait to be discovered as well. Hopefully the New Horizons spacecraft can help find them if they do exist, when it reaches Pluto in 2015.