Even though it's no longer considered a planet, Pluto still excites the imagination as it skims the outer reaches of our solar system.
But there's a lot we didn't know about Pluto until relatively recently (beside the fact that it isn't actually a planet). For example, it has not one, but several, moons.
Astronomy contributor Jean Creighton offers up five facts you didn't know about Pluto and its orbiting masses.
- Pluto was named in 1930 by an 11-year-old girl named Venetia Burney of Oxford, England. It was almost called Minerva or Vulcan.
- Its biggest moon, Charon, is almost as big as Pluto. It was the first moon to be discovered, in 1978.
- Two other moons, Nix (which means "night") and Hydra (after the mythical multi-headed monster killed by Hercules) were discovered in 2005, shortly after the Hubble Space Telescope went up.
- In 2011 and 2012, two more moons were discovered. After considering a list of 21 names, all related to Greek myths and the "underworld," a committee chose "Kerberos" (after the mythical three-headed dog gate-keeper) and "Styx" (after the river bordering Earth and the underworld).
- A spacecraft called New Horizons is on its way to Pluto right now, and should arrive by July 14, 2015. It left in 2006, and is expected to travel within 8,000 miles of Pluto, to give a closer look at the former planet and its moons - most of which weren't discovered until after the craft was already on its way.
Jean Creighton is the director of UW-Milwaukee's Manfred Olson Planetarium, and is our regular astronomy contributor.