Names from Greek mythology’s underworld have been given to Pluto’s fourth and fifth moon, discovered in 2011 and 2012, the International Astronomical Union (IAU) announced earlier this week.
As announced by the IAU, the moon formerly known as P4 is now Kerberos, named after the many-headed dog that guarded the entrance to the underworld in Greek mythology.
Moon No. 5 is Styx, named for the river that souls had to cross over to get to Hades, or the underworld, and the goddess who ruled over it.
Names from Greek mythology are not new to the Plutonian family, that counts five moons that circle Pluto. In Greek mythology, Pluto, also known as Hades, was the lord of the underworld.
Pluto’s other moons are Charon, named for the ferryman who carried dead souls across the river Styx; Hydra, a multi-headed monster that helped guard the entrance to the underworld; and Nix, the mother of Charon.
Kerberos and Styx were discovered by a team led by Mark Showalter of the SETI Institute, using the Hubble Space Telescope. It is estimated Kerberos and Styx are the smallest of Pluto’s moons so far.
By astronomical tradition, the discoverer of a new planet or moon is entitled to suggest names for it to the IAU. This time, however, an open contest was held for the input of general public.
Name Cerberus was later changed to the Greek spelling Kerberos to avoid confusion with an asteroid that already exists under this name.
“The IAU rules ensure that the names work across different languages and cultures in order to support collaborative worldwide research and avoid confusion,” the Union said in a statement.
Once known as the ninth planet of the solar system, in 2006 Pluto was classified as a dwarf planet, due to the fact its orbital path is cluttered with thousands of small icy objects.