Our New Solar System

Three days ago in Prague, the International Astronomical Union voted on and passed a new definition of Planets, which demotes Pluto to a new classification of Dwarf Planet. The actually definition for a Planet is:

"A “planet” is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit."

Which means our solar system is now made up of 8 planets, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. The IAU also defined a new classification: a dwarf planet. The formal definition is:

"A “dwarf planet” is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape , (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite."

Which means Pluto, Ceres and 2003 UB313(nicknamed Xena) are the first dwarf planets. The IAU also defined all other objects except satellites orbiting the Sun shall be referred to collectively as “Small Solar-System Bodies”.

Now I have been reading articles and blog posts objecting to the demotion of Pluto from full Planet status. Whats the big deal. Pluto has never enjoyed full planetary status since it was discovered about a hundred years ago. It's about time they finally classified it.  Our knowledge of the Universe and especially our Solar System is growing, so why can’t our classifications change also. 

Anyways, this classification could change in the future, depending on what data the New Horizons spacecraft sends back to earth.  The spacecraft lifted off in January of this year, at the time headed for the ninth planet, now it is headed for the first Dwarf Planet.  Who know what we will have learned by then. We might have to except more of that horrible ... "change".