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Hello folks.

Question about the definition of a planet. Looking on the NASA website it states that a planet must be orbiting a star, which is a bit embarrassing for rogue planets.

This seems like an obvious mistake so why is it used? Were they trying to write the rules to differentiate moons and planets?

Thank you.

I’d recommend checking out the Wikipedia entry. It goes through the history of the definition.

Here you go, something only partially useful.

Wookiepedia Definition of a Planet

And something actually useful:

Astronomers Propose We Change The Definition of 'Planet' - Here's Why

Thanks folks.

From what I can gather it’s still a bit hazy.

It's likely hazy because in the grand scheme of things it doesn't matter right now. Pluto being a plant or a dwarf planet or a planetoid or whatever doesn't really impact life on earth. Even in the sciences it really only affects a classification system and the number of planet/planetlike bodies we can reach is utterly tiny.

So the terms can wriggle around a lot.
Furthermore its an area where we honestly know very little and new stuff is being found all the time. So some of the haze is just the evolving of the field of study and the shifting interpretations/understandings and classifications that arise from that.



Heck even in thing we have studied for generations like animal species, there are still variations even within the latin naming schemes. Not to mention that even without politics/national variation and so on - you've got DNA re-writing huge chunks of classifications

The short version is that the old definition of planet would have included things like Ceres, which is the largest object in the asteroid belt - and clearly not a planet as we understand it. They had to change the definition to exclude Ceres, which also wound up excluding Pluto as a side effect.

Basically, Pluto was collateral damage.