Au revoir , Pluto In this newly revised, bestselling backlist title, beginning readers and budding astronomers are launched on a wild trip to visit the now eight planets in our solar system (per the International Astronomical Union's 2006 decision to downgrade Pluto from a planet to a dwarf planet), along with the Cat in the Hat, Thing One, Thing Two, Dick, and Sally. It's a reading adventure that's out of this world