Re: Not a planet?
The IAU definition is: is in orbit around the Sun, has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and has "cleared the neighborhood" around its orbit. Pluto fails the last of these.
If you remove the last requirement then Pluto becomes a planet again ... but so do very many other objects, perhaps a hundred or so. So I think the idea is to keep the number of things we call 'planets' fairly small while having some criteria other than 'Joe says it's a planet' for what a planet is.
But it's just words: Pluto doesn't care what we call it.