Hydra (moon) the Hydra, the nine-headed serpent that battled Heracles in Greek mythology. The nine heads of Hydra are a reference to Pluto's tenure as the ninth planet; its initial, "H", refers to the Hubble Telescope, which discovered Hydra and, together with Nix, to the "New Horizons" mission whose safe passage was the motivation for taking the Hubble images. Hydra orbits the barycenter of the system in the same plane as Charon and Nix, at a distance of about 65,000 km. Its eccentricity of 0.0059 is small, but significantly non-zero, and the largest of those of Pluto's small moons (slightly larger than
Phthius (mythology) Phthius (mythology) In Greek mythology, Phthius (Ancient Greek: φθῖος) was the name of two different figures: Phthius, son of Lycaon. Together with his father and the rest of his brothers (except Nyctimus), Zeus slayed them with lightning because they tried to serve the god with human flesh.""Lycaon, reigning over the Arcadians, begat by many wives fifty sons, to wit: Melaeneus, Thesprotus, Helix, Nyctimus, Peucetius, Caucon, Mecisteus, Hopleus, Macareus, Macednus, Horus, Polichus, Acontes, Evaemon, Ancyor, Archebates, Carteron, Aegaeon, Pallas, Eumon, Canethus, Prothous, Linus, Coretho, Maenalus, Teleboas, Physius, Phassus, Phthius, Lycius, Halipherus, Genetor, Bucolion, Socleus, Phineus, Eumetes, Harpaleus, Portheus, Plato, Haemo, Cynaethus,