The distant, icy dwarf planet Pluto gets a new moon, and the new Horizons Mission to Pluto has a new target when it visits the system three years hence:

HST— The Pluto team is intrigued that such a small planet can have such a complex collection of satellites. The new discovery provides additional clues for unraveling how the Pluto system formed and evolved. The favored theory is that all the moons are relics of a collision between Pluto and another large Kuiper belt [1] object billions of years ago.

Pluto’s largest moon, Charon, was discovered in 1978. Hubble observations in 2006 uncovered two additional small moons, Nix and Hydra. In 2011 another moon, known as P4, was found in Hubble data.Provisionally designated S/2012 (134340) 1, or P5, the latest moon was detected in nine separate sets of images taken by Hubble’s Wide Field Camera 3 on 26, 27 and 29 June, and 7 and 9 July 2012.

I asked principal investigator Alan Stern, how will New Horizons, currently speeding across the outer solar system and nearing the orbit of Neptune, get much of a look at such a tiny object as it flashes by? His response then is even more relevant now:

Alan Stern— We planned ahead; we didn’t want a ‘weekend at Pluto’ kind of a mission. But since we’ll be moving about 14 kilometers a second when nearing Pluto’s orbit and Pluto will be orbiting at about 5 km/s roughly across our line of motion, we had to design our instruments to allow us to study the Pluto system for months on approach — which means being able to start their studies at very great range. So we had to pick the right kind of cameras and other instruments, with the right kind of focal lengths and other properties. And we did that! So as a result, we’ll be studying the Pluto system for months and months on approach.In late 2014, we will be able to finally resolve Pluto as a disk. But the resolution improves geometrically from there. The real fun starts in the spring of 2015, when we sort of open the big shutters and start collecting images better than anything we have now—even from the Hubble Space Telescope’. Finally, on July 14th, 2015, we sail right through the Plutonian system, inside of the orbit of its largest satellite Charon. We’ll also map and study two other, smaller moons of Pluto, Hydra and Nix, during this time. Then we’ll be capturing more images and data on the way out. So the actual observation period will be almost 6 months.

2015 will be quite a year in dwarf planetary astronomy! Not only will we get out first close up pictures of mysterious Pluto, NASA’s Dawn Spacecraft will also visit the dwarf planet Ceres and return detailed images of that world.