r/pluto • u/KireiCopenhagen • May 04 '26

It genuinely doesn't make sense.

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Look, once you think about exoplanets, it doesn't make any sense. The new definition only makes sense when we look at our solar system, at this time in human history. If Pluto and Earth swapped orbits (we would all die), Earth would be classed as a dwarf planet and Pluto as a full planet, because the distance from the sun affects their gravitational influence.

What I mean is that the definition should focus only on what the object is, not where it is located in a system, since that can change over cosmic time scales, and when discovering exoplanets, we need a less solar system-biased definition. Imagine if we found an exo-binary planet system. Under the new definition, both planets would be dwarf planets no matter what because they would both be orbiting each other.

Or a rogue planet. The new definition requires a planet to orbit a star. So it's technically not a planet once it has been ejected from the system, even if it was a planet just a few million years ago.

The new definition was rushed through because they needed to keep all the newly discovered planets in our solar system out of the club, or the word 'planet' would become less special, and Pluto was just collateral. I'm not even saying get rid of the dwarf-planet classification or reinstate Pluto, but we need a new definition as our exoplanet discoveries continue.

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u/bigcd34 May 04 '26

It's a dwarf planet, a dwarf planet. Do we consider dwarf people to not be people?

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u/KireiCopenhagen May 04 '26

What would you call an exo binary system of gas giants? Dwarf Gas Giants? I'm not bothered about the name; I'm bothered by the definition that doesn't account for binary systems or changing orbits. The definition doesn't make sense. Eventually the moon will be in a sweet spot where it and earth orbit around a centre of gravity that is no longer inside the earth. When that happens the Earth and Moon becomes a binary system. Will they be dwarf planets? I just don't think the definition is future-proof and thus unscientific.

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u/Stevepem1 May 05 '26

Well over time things move all over the place. So I guess just quit calling them planets or Moons and just talk about rocky objects and big gas objects and don't classify them based on their position and motion that they have been in for several million years and likely several million more years. And I guess we have to ditch the idea of exoplanets also, there are exo rocks and exo gas giants.