A team led by Hal Weaver and Alan Stern announced that Hubble Space Telescope images taken in May had revealed two previously unknown moons circling Pluto, then still classified as the ninth planet. The moons, roughly 5,000 times fainter than Pluto itself, were provisionally designated S/2005 P1 and P2 before later being named Hydra and Nix.
The discovery came at a pivotal moment for Pluto's scientific reputation, just a year before the International Astronomical Union would controversially strip it of full planetary status and reclassify it as a dwarf planet. Finding two additional moons orbiting a body once thought to be a simple, lonely world orbiting alone with only its large companion Charon suggested a far more complex system than astronomers had assumed.
The timing proved fortunate for NASA's New Horizons mission, launched in January 2006 to fly past Pluto; mission planners were able to incorporate observation plans for the newly discovered moons before the spacecraft's actual flyby in July 2015. When New Horizons finally sent back images a decade later, both tiny, irregularly shaped moons were revealed in detail, elongated bodies just tens of kilometers across, tumbling chaotically through Pluto's distant, icy neighborhood.