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 in popular culture to name its equipment such as the Nike missile project and the Navy having over a dozen ships named from Greek mythology. Greek mythology has been the source for names for a number of ships in the British navy as well as the Australian Royal Navy which has also named a training facility in Victoria called HMAS Cerebus. The Canadair CP-107 Argus of the Royal Canadian Air Force is named in honor of both the hundred eyed Argus Panoptes the "all seeing" and Odysseus' dog Argus who was the only one who identified Odysseus upon his return home. Many celestial