So, in school (that's a long time age) they have been teaching us there are 9 planets in our solar system.
But every now and then I keep reading stories about another "dwarf planet" (Eris, discovered in 2005) that - depending on what source tells the story - is another planet according to the astronomical definition, while other sources say that it isn't a planet. Some even say Pluto isn't a planet anymore either.
The result: I'm confused due to the contradicting stories. Even Wikipedia isn't clear about Eris and only writes (emphasis mine):
NASA initially described it as the Solar System's tenth planet.
Initially? So, is it a 10th planet or not? Fact is, there is another "something" out there and it surely seems to look like a planet. Yet, some people keep stating there are 9 planets in our solar system, while others say there are more than 9 planets, and then again there are people stating that the latest definition of "planet" has kicked out Pluto too so there are actually fewer than 9 planets in our solar system.
Trying to get a definite, official, and astronomically correct answer I can actually rely on, I'm therefore asking: How many planets are there in this solar system?
The "Definition of planet" at Wikipedia doesn't really help either, as it states:
Many astronomers, claiming that the definition of planet was of little scientific importance, preferred to recognize Pluto's historical identity as a planet by "grandfathering" it into the planet list.*
* Dr. Bonnie Buratti (2005), "Topic — First Mission to Pluto and the Kuiper Belt; "From Darkness to Light: The Exploration of the Planet Pluto"", Jet Propulsion Laboratory. Retrieved 2007-02-22.
So, if you link somewhere to provide proof, it would be great if you could point me to a more trusted source than Wikipedia. Ideally, an astronomical trusted source and/or paper.