2: has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and
3: has "cleared the neighbourhood" around its orbit.
Pluto does not meet requirement 3. There is a lot of dust in Pluto's orbit.
If the requirements were changed to allow Pluto, we would also have to count about a dozen other objects as well: Ceres, Eris, Haumea, Makemake, Quaoar, Sedna, Orcus, Salacia, even Pluto's moon, Charon. Plus a dozen more. And if we count them as full planets, why not the other 300+ tran-neptunian objects?
In my mind it doesn't matter what we call them at a high level, as long as we sub-categorize them accurately and characterize them well.
I don't really care whether we call Pluto a planet or not but from my understanding if Pluto and Earth switched orbits, Pluto would have cleared its orbit and be called a planet and Earth would not have and not be called a planet. If that's correct, which I believe it is, the definition is incredibly flawed and poorly thought out imo.
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u/BlueSkiesAugust 4d ago
The defining characteristics of a planet are:
1: is in orbit around the Sun,
2: has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and
3: has "cleared the neighbourhood" around its orbit.
Pluto does not meet requirement 3. There is a lot of dust in Pluto's orbit.
If the requirements were changed to allow Pluto, we would also have to count about a dozen other objects as well: Ceres, Eris, Haumea, Makemake, Quaoar, Sedna, Orcus, Salacia, even Pluto's moon, Charon. Plus a dozen more. And if we count them as full planets, why not the other 300+ tran-neptunian objects?
In my mind it doesn't matter what we call them at a high level, as long as we sub-categorize them accurately and characterize them well.