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Originally Posted by dammage79
I just said I was no scientician! So now I have to hone my own parameters to better make my argument. Atmosphere should be a requirement, perhaps your own moon could also make a solid argument.
I don't think there's anything bigger or close to Pluto in the asteroid belt between Mars and Jupiter and the Kuiper belt probably has some other hidden gems on there too. I love the fact they're sending New Horizons on deeper into the Kuiper belt to focus on some other larger objects as well. But they're just on the outside of the Suns gravity no?
I thought Pluto was right on the bleeding edge of that.
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Not sure why an atmosphere should be a requirement. Mercury barely has an atmosphere to speak of, and Pluto does have an atmosphere, though it too is very thin.
As for being outside the sun's gravity, if the Kuiper belt objects were outside the sun's gravity then there wouldn't be a kuiper belt. Technically the sun's gravity extends infinately, but if you are talking about the point at which it is no longer the dominant force, that extends well beyond the Kuiper belt. The Oort cloud extends up to 2 lightyears out, so we are nowhere near that boundry when we are talking about Pluto.
As for the Planet/not planet argument, there are other requirements other than/more important than size, one of which is that it has cleared the general vicinity of it's orbit, hence nothing in the asteroid belt is a planet because it's part of a region of general rubble that isn't domiated by one body, kind of like how Pluto is a part of the Kuiper belt, a collection of bodies that sort of occupy the same region.
In the end it's all semantics as it doesn't change what we can learn from visiting these places.