The Solar System.  You know it, you love it, you've made copies of it from Styrofoam and Magic Markers.  Nine planets, a ring of asteroids, and some left over debris in the form of comets and bric-a-brac.  

Now get ready to change your thinking.

For centuries, people recognized five wanderers among the circling stars: Mercury, Venus, Mars, Jupiter, and Saturn.   The introduction of the telescope added Neptune, Uranus, and finally tiny Pluto.  And a billion textbooks later, those eight, along with Earth, define the standard nine planets.  However, almost from the moment of it's discovery, Pluto has been "on the bubble."  It's too small, and it's orbit is too quirky.  For decades, some astronomers have wanted to kick it out of the planet club.  Only that raised ne