Hydra is the second outermost known natural satellite of Pluto. It was discovered along with Nix

Nix (moon)

Nix is a natural satellite of Pluto. It was discovered along with Hydra in June 2005, and is to be visited along with Pluto by the New Horizons mission in July 2015.- Discovery :...

 in June 2005, and is to be visited along with Pluto by the New Horizons

New Horizons

New Horizons is a NASA robotic spacecraft mission currently en route to the dwarf planet Pluto. It is expected to be the first spacecraft to fly by and study Pluto and its moons, Charon, Nix, Hydra and S/2011 P 1. Its estimated arrival date at the Pluto-Charon system is July 14th, 2015...

mission in July 2015.
Hydra was found by the Hubble Space Telescope's

Hubble Space Telescope

The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...

 Pluto Companion Search Team, which is composed of Hal A. Weaver, Alan Stern

Alan Stern

S. Alan Stern is an American planetary scientist. He is the principal investigator of the New Horizons mission to Pluto....

, Max J. Mutchler, Andrew J. Steffl, Marc W. Buie

Marc W. Buie

Marc W. Buie is an astronomer at Lowell Observatory in Flagstaff, Arizona. He grew up in Baton Rouge, Louisiana and went on to get a B.S. in Physics from Louisiana State University in 1980. After that he switched fields and earned his Ph.D. in Planetary Science from the University of Arizona in...

, William J. Merline, John R. Spencer, Eliot F. Young, and Leslie A.