gives planetary status to boring rocks like Mercury but denies it to fascinating worlds like Titan It also denies planethood to any potential rogue planets The most all inclusive definition which is favoured by astronomers like Mark Buie is that a planet is anything big enough to be round but not big enough to fuse hydrogen This would basically mean that any object discovered in the universe from about a fifth the mass of our Moon to about 13 times the size of Jupiter is a planet It would mean that kids would have to give up learning the planets in our Solar System since the number would go from eight to about 50 And that is the main issue The word planet is not a scientific term it s a term tied to myth history and religion It s special Is it right that tiny bits of ice at the end of the Solar System should be so honoured or should the term planet be selectively bestowed only on those that deserve it This isn t a scientific issue but then planet has never been a scientific word That s actually a pretty good definition but I think you should add or at least state more explicitly that planets have to orbit the sun directly i e a planet is not a satellite This is not about how interesting something is Britney Spears is interesting but she does not fit the definition I have made for music that I like to listen to Another good addition I believe would be to mention that planets must be unique that is there should not be an abundance of like objects think Kupier belt in the immediate vicinity And finally if the definition of a planet is not a scientific issue then the IAU a scientific organization should leave the definition to people in linguistics like the Oxford English Dictionary Your definition is basically the one the IAU chose to adopt As for why they did it in the first place they didn t have a choice They kept under the rug for as long as they could then Eris turned up and everything went crazy Believe me they didn t want to do it Eris forced their hand You re right but I think the IAU should have worded the definition differently Cleared the neighborhood is a little ambiguous One of the articles dealing with this controversy mentions that Earth Jupiter etc have not cleared their neighborhoods either but the phrase actually refers to the original creation process Unique in my opinion is a bit less ambiguous open for interpretation I m moving this here since it really doesn t belong on the article s talk page Unique isn t really any less ambiguous than clearing the neighborhood No planet is truly unique each shares its orbit with dust particles micrometeoroids the occasional comet and many other things If you read the clearing the neighborhood article you ll see that Steven Soter has developed a perfectly acceptable mathematical definition for clearing the neighborhood that creates a sharp division between the large and small objects in the Solar System That s what I meant The mathematical definition is less easily definable in layman s terms than unique as in no objects resembling it in the immediate vicinity Resembling it how In size shape and composition For instance Pluto resembles Kupier belt objects but Earth does not resemble Venus And what I meant when I said that the IAU should have worded their definition differently was that to someone who had not heard of the mathematical formula or read the article Clearing the neighborhood could have referred to the present or the time of formation Earth and Venus resemble each other rath