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 frigate Hydra delivered to the Hellenic Navy on 15 October 1992 and first sailed in Greek waters on 28 January 1993. The crest of the frigate "Hydra" is the same as that of her predecessor. It is based on one of the flags which the ships of Hydra sailed under during the 1821 revolution. In April 1988, the Hellenic Navy proposed and approved the four frigates of the MEKO 200 type in an effort to modernize its fleet. After a lengthy negotiation process, the following contracts were signed to fulfill the program: Greek frigate Hydra Hydra" (F-452) (Greek Φ/Γ "Ύδρα) is the