Hydra (moon)

Hydra, formal designation (134340) Pluto III, is a <a href="/facts/Moons_of_Pluto/g89834mJ">natural satellite of Pluto</a>, with a diameter of approximately 51 km (32 mi) across its longest dimension. It is the second-largest moon of <a href="/facts/Pluto/egq7MBeR">Pluto</a>, being slightly larger than <a href="/facts/Nix_(moon)/Qf3qsr7m">Nix</a>. Hydra was discovered along with Nix by astronomers using the <a href="/facts/Hubble_Space_Telescope/NQeIf0vw">Hubble Space Telescope</a> on 15 May 2005, and was named after the <a href="/facts/Lernaean_Hydra/CQcBcyIq">Hydra</a>, the nine-headed underworld serpent in <a href="/facts/Greek_mythology/M7k4FvW8">Greek mythology</a>. By distance, Hydra is the fifth and outermost moon of Pluto, orbiting beyond Pluto's fourth moon <a href="/facts/Kerberos_(moon)/b0X5ssTS">Kerberos</a>.
Hydra has a highly <a href="/facts/Albedo/TJDRdKEB">reflective</a> surface caused by the presence of <a href="/facts/Ice/BGvkKFjD">water ice</a>, similar to other Plutonian moons. Hydra's reflectivity is intermediate, in between those of Pluto and <a href="/facts/Charon_(moon)/elazjsMp">Charon</a>. The <a href="/facts/New_Horizons/G5XTU5DK">New Horizons</a> spacecraft imaged Pluto and its moons in July 2015 and returned multiple images of Hydra.

Hydra (moon) open-in-new

Hydra (moon)