Image of Neptune moon, Hydra, taken by New Horizons

Since its discovery in 2005, Pluto's moon Hydra has been known only as a fuzzy dot of uncertain shape, size, and reflectivity. Imaging obtained during New Horizons' historic transit of the Pluto-Charon system and transmitted to Earth early this morning has definitively resolved these fundamental properties of Pluto's outermost moon. Image Credit: NASA-JHUAPL-SWRI


Hydra was discovered in June, 2005 by Hal Weaver and a large team of astronomers using the Hubble Space Telescope.

In Depth

Hydra is the outer of the two moons discovered orbiting Pluto in 2005. Nix and Hydra are roughly 5,000 times fainter than Pluto and are about two to three times farther from Pluto than its large moon, Charon, which was discovered in 1978. Nix and Hydra are roughly 20 to 70 miles (32 to 113 km) wide.

They are so faint so small and so faint that scientists combined a short exposure of Pluto and Charon and a long exposure of Nix and Hydra to create images of them all together.

How Hydra Got its Name

Hydra was named for the nine-headed serpent that Hercules fought in Greek and Roman mythology.

Pluto News