Hydra and Nix are the names of Pluto’s newfound moons, announced the International Astronomical Union (IAU) June 21. The moons, discovered in May 2005 were previously called S/2005 P1 and S/2005 P2, respectively.
In Greek mythology, Hydra is a nine-headed monster with a snake’s body that guards the entrance to Hades, and Nyx is the goddess of night. The names are especially appropriate because Pluto is the ninth planet and named for the god of the underworld. Because asteroid 3908 is already named Nyx, the IAU changed the spelling for Pluto’s moon to an Egyptian equivalent, Nix.
“You’re going to be hearing a lot more about Nix and Hydra in coming years — astronomers are already applying for telescope time to study their orbits and physical properties. And when New Horizons flies by Pluto in the summer of 2015, each will be mapped in detail,” says Stern, also New Horizons’ principal investigator.