13 PlanetsBy: David A. Aguilar First, Pluto left. Then it came back, along with Ceres and Eris and now Haumea and MakeMake, too! The recent actions of the International Astronomical Union have put every solar system book out of date. In response, National Geographic joins forces with David Aguilar of the Harvard Smithsonian Astronomical Observatory to revise our 2008 bookand to update young readers on the high interest topic of space. Using simple text and