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
Greek mythology Greek mythology Greek mythology is the body of myths originally told by the ancient Greeks. These stories concern the origin and the nature of the world, the lives and activities of deities, heroes, and mythological creatures, and the origins and significance of the ancient Greeks' own cult and ritual practices. Modern scholars study the myths in an attempt to shed light on the religious and political institutions of ancient Greece and its civilization, and to gain understanding of the nature of myth-making itself. The Greek myths were initially propagated in an oral-poetic tradition most likely by Minoan and Mycenaean singers