The IAU screwed up their planet definition 13 years ago today, but we've learned that dwarf planets like Pluto are full-fledged planets, &, numbering over 120, the most common type of planet, ahead of giants & terrestrials. @AlanStern @DrPhiltill @carolynporco @plutokiller
Is the moon a planet? If yes, you have a self-consistent argument that “planet” just means “round thing.” If no, you agree that the dynamics of the orbit are part of the definition.
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Phil's got the historical argument. Coming from the modern planetary science community, yes, moons are planets. I usually call them "planetary bodies" but sometimes I slip & call them planets and don't feel technically incorrect.
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Phil's historical document mentions major planets, secondary planets and minor planets. You're lumping major planets and secondary planets but leaving out minor planets as "planets." None of this includes the notion of "round." Also ignores the history of Ceres.
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Yes, coincidentally I just tweeted about that recently, here:https://twitter.com/drphiltill/status/1164974752215252995?s=21 …
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I’ve been exhaustively reading the scientific literature about this from Galileo until now. Large moons have always considered planets. In the 1800s the two small moons of Mars were found & astronomer R. Proctor argued they aren’t true secondary planets becoz they’re too small.
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Planets orbit stars. Moons orbit planets. Planets & moons are worlds. An icy moon like Triton resembles dwarf planet Pluto since they are also icy worlds. The terms "planet" & "moon" take nothing away from the inherent structure of a world. "Dwarf" is a descriptor not an insult.
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