Meet the newest kids in the solar system: Nix and Hydra. The pair of moons orbiting Pluto were officially christened last week by the International Astronomical Union, which is in charge of approving celestial names.
Until last year, scientists thought Pluto was accompanied by only one moon, Charon. But the Hubble Space Telescope spotted the two satellites. The duo had been known by the tongue-twisting names S/2005 P 2 and S/2005 P 1.
Earlier this year, the moons' discoverers, led by Alan Stern of the Southwest Research Institute in Boulder, submitted their choices to the IAU.
The names, with roots in Greek mythology, were selected in part because the first letter of each, 'N' and 'H,' were a tribute to the New Horizons spacecraft, Stern said.
New Horizons blasted off this year on a nine-year mission to study Pluto, the last unexplored planet in the solar system.