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 Greek frigate Hydra Hydra" (F-452) (Greek Φ/Γ "Ύδρα) is the lead ship of the Greek and flagship of the Hellenic Navy. The ship was built in the same shipyard as the Blohm + Voss MEKO 200 frigate class, on which its design was based. Three more vessels were built by Hellenic Shipyards Co. at Skaramagas in following years. It is the fifth ship in the Hellenic Navy to bear the name "Hydra". "Hydra" was the first of four frigates of the MEKO 200 type (the four being "Hydra", , , and ) ordered by the Greek government. The ship was