Quick - what's wrong with the above picture? It's a diagram of the Solar System - the kind of thing we've seen in our textbooks and used for...oh, about the past 75 YEARS. Nine planets in the Solar System - just one of those givens we all know and love. But yeah, as you've probably heard, it's now out of date.
So what changed? Was a new planet discovered? Confirmation of a tenth planet, newly discovered? No, not so much. Instead, "they" (the IAU) voted today to change the definition of a planet. Yes, you read that right, change the definition of a planet. APPARENTLY scientists have been pretty unhappy about Pluto being included in with the rest of the planets for quite some time now. It's too small, too barren, it's got a funny orbit... it doesn't fit in with the cool kids. And what do we do with things which don't fit in? Why, ostracize them, of course! We give it the astronomical equivalent of making it ride on the short bus, out of sight and out of mind for all the normal kids. So, thanks to the eggheads, Pluto is now no longer a planet. Instead, it's newly demoted to a new "dwarf planet" status, which it'll have to share with at least two other things, with quite a few other likely candidates soon to join it, pending "approval". They resolved the following:
The IAU...resolves that planets and other bodies in our Solar System be defined into three distinct categories in the following way:This whole process the IAU has been going through for changing the definition of a planet actually went through several stages... at one point it was even seeing more likely that we'd have TWELVE planets instead of 9. Or even more than 50! Obviously that'd never work... so instead we LOSE a planet.
(1) 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.
(2) 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.
(3) All other objects  except satellites orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".
Needless to say, the backlash started pretty quickly. There's bumper stickers, shirts, and some good stuff in a Worth 1000 photoshop contest. I'm sure more is already on it's way.
Still... this isn't the FIRST time that Pluto's gotten the short end of the stick anyway - so this shouldn't come as THAT big of a surprise. After all, among the whole group, he was the only one who couldn't walk upright, wear clothes, or speak English....