The discovery images were taken on May 15, 2005 and May 18, 2005; the moons were independently found by Max J. Mutchler on June 15, 2005 and Andrew J. Steffl on August 15, 2005. The discoveries were announced on October 31, 2005, after confirmation from photographs archived in 2002. The moon were designated S/2005 P 1 (Hydra) and S/2005 P 2 (Nix).