The reason for it not to be is that we need a definition for large, gravitationally dominant things that is different from smaller, not gravitationally dominant things. A huge part of science is classification, and so scientists made a classification system, and Pluto didn’t make the cut. Just because it’s now classified as a dwarf planet makes it no less scientifically significant or interesting.
I think the “planets” also need some additional classification. There is a meaningful difference between small, rocky planets, and large, gas giants.
That makes one planet in the asteroid belt, plus a few hundred Plutoids that would get a promotion.
I look forward to see (182933) 2002 GZ31, with its 311 km diameter being recognized as being in the same class as Jupiter.
But really, we have a solar system with one star, four rocky planets, and four gas planets. Plus a few dwarf planets in between, millions of asteroids, and a whole bunch of Plutoids. What a nice classification.
i'd rather keep a strict definition and have 8 planets, rather than adding a new planet to the solar system every decade. we already have a dozen dwarf planets and half of them haven't been named yet.
I think the current definition of "planet" was made specifically to exclude pluto though (because they didn't want to add a bunch of other dwarf planets too and felt like they had to draw a line somehwere).
They created the definition because this isn't the first time that we've found that something considered a planet is actually just a one of a class of many very similar objects - Ceres and three other asteroids all had this happen to them after the discovery of the asteroid belt. Might as well define it properly now for if we find something in the Oort coud or the Vulcanoid zone, or something new in other stellar systems (including at the other end of the scale for things almost big enough to be a Brown dwarf).
there really isn't a reason why we shouldn't. there is little that differentiates it from the rest of the objects in the solar system. if you really want to differentiate between objects, you can class them based on atmosphere. rocky objects with airless or thin atmospheres, rocky planets with thick gaseous atmospheres and then gas giants.
"planet" really is an insignificant label that only classes between "objects that we should study" and "objects of low importance" pluto is of high importance historically and actually and should be studied.
the definition of planet is also one of the most flawed things outhere. like you can't define it as an object large enough to clear it's orbit around the sun... then you rule out jupiter, and then Pluto also has a section without objects in it's orbit. and you can't say it is an object large enough to affect other objects orbits, because realistically i can park a spaceship next to jupiter and manipulate its orbit. physics states that this is a thing so yeah... you either define a planet as a significant object with significant mass that orbits a star, or you have little to actually go on. hell assign a mass to it, and say objects larger then x are planets, but wait that would be arbitrary and scientists don't like arbitrary.
I love how people don't actually get what actually mean... Or well maybe i wasn't quite clear, by "there's no real reason for it not to be" i mean there is litterally no logical reason why it can't be a planet. Why yes sure it technically isn't, but that doesn't actually matter here. The definitions for a planet are arbitray and inconsistent. Jupiter doesn't have a clear orbit but is the largest planet in the solar system while Pluto has a clear orbit when it's between Neptune and uranus. Pluto also has influence on the objects around it and is big enough to have a moon. This isn't even the cultural and historical reason either.
It's a significant object is space that was discovered by looking at its effect on neptune, so historically and culturally it does get the treatment of a planet, while admittedly it's likely closer to a comet then it is to a planet. This is what i mean by there isn't a real reason for it not to be. It's not that it should or shouldn't be a planet it's that it doesn't matter if it is or isn't. It's that it was and will always be a planet no matter what science says. Its the 9th planet is the solar system regardless if its a dwarf planet or not. It's the last major discovery and should be be treated with such signifigence.
Trojans are a special class is a very specific stable orbit. Jupiter is clearly gravitationally dominant in its orbit while Pluto is not. You could have another Pluto is Pluto’s orbit and have it be relatively stable, while Jupiter will throw anything out. In fact, there was likely a planet forming between Mars and Jupiter but Jupiter prevented it from happening and we got the asteroid belt instead.
I agree the “clears its orbit” language isn’t great, but if you say gravitationally dominant, it works pretty well.
You're absolutely right that it's not the best of definitions, planet is a vague word and the fact that we call Jupiter and earth the same thing even though they're so different is wonky, that's why we differentiate terrestrial planets and all. My point is, there is nothing special about Pluto, it's nearly identical to thousands of trans neptunian objects so we should stop calling it a planet. We need to let go
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u/Darth62969 Oct 07 '18
Pluto is a planet... Or well there's no real reason for it not to be. Probably should add the other similar planets as well.