Yea!!!! Pluto is a planet after all! I knew it all the time. Moreover, with the International Astronomical Union (IAU)'s expected new ruling Ceres will regain it's status as a planet too. Along with the addition of Charon and 2003 UB313, a Kuiper Belt object. Soon there will be more planets added to the list since the new (actually the first unambiguous) definition of a planet will qualify nearly 50 more Kuiper Belt objects.
The new definition takes into account several criteria and matches them against each other to come up with a definite set of rules for classifying a planet. Size, gravitational forces, orbit around a star versus another planet, are just a few of the criteria. What I like most is that one criterion classifies Pluto and Charon as binary planets rather than a planet and moon. Something that I have brought up in the past with friends who are amateur astronomers too. The two clearly orbit each other and not one around the other like our moon orbits earth.
However, the proposed rules also draw a line between common asteroids and smaller planets. The issue of gravity. At some point, an object reaches sufficient mass that its own gravity overcomes the shape that the rubble it is made from would naturally take. In other words, rather than being oblong or some other shape because of uneven lumping, gravity causes it to take a more uniform shape, basically round or near round. This is not to say that an asteroid can't be round, but rather asks "is it round because it formed round or does its own gravity cause it to be round?" Not a trivial thing in the scope of stellar bodies.
Gravity also comes into play in whether the object orbits a star or another stellar object or is part of a binary pair. Everything has a center point of gravity in relation to its neighbor. If that center point of gravity is between them out in space, they are binary. If that point is within one of the objects then one is a satellite of the other. Things that orbit stars are planets, things that orbit planets are moons.
I hope that the full union will approve the IAU's new proposal and then we can all say we were there when the 12th planet and possibly more were discovered. Something no one has been able to say since 1930.