• Neato@ttrpg.network
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    6 months ago

    It’s not the size that counts but the ability to clear your orbit. ;)

      • Neato@ttrpg.network
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        6 months ago

        Good question! I had forgotten about Jupiter’s Trojans and Greek asteroids!

        I went and checked the definiton of Clearing the Neighborhood by IAU, emphasis mine:

        The phrase refers to an orbiting body (a planet or protoplanet) “sweeping out” its orbital region over time, by gravitationally interacting with smaller bodies nearby. Over many orbital cycles, a large body will tend to cause small bodies either to accrete with it, or to be disturbed to another orbit, or to be captured either as a satellite or into a resonant orbit. As a consequence it does not then share its orbital region with other bodies of significant size, except for its own satellites, or other bodies governed by its own gravitational influence. This latter restriction excludes objects whose orbits may cross but that will never collide with each other due to orbital resonance, such as Jupiter and its trojans, Earth and 3753 Cruithne, or Neptune and the plutinos.[3] As to the extent of orbit clearing required, Jean-Luc Margot emphasises “a planet can never completely clear its orbital zone, because gravitational and radiative forces continually perturb the orbits of asteroids and comets into planet-crossing orbits” and states that the IAU did not intend the impossible standard of impeccable orbit clearing.[2]

        Trojans and Greeks orbit Jupiter’s LaGrange points in a stable orbit and so they are governed by Jupiter’s gravity. You could say they’re really weird moons orbiting semi-stable points Jupiter creates.

    • affiliate@lemmy.world
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      6 months ago

      this condition makes “planetness” into a local condition. so theoretically, we can throw enough junk into space and stop anything we want from being a planet.

      pluto just got unlucky in terms of the amount of trash it has in its way. its not fair :(

        • DigitalDruid@lemmy.sdf.org
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          6 months ago

          Bad astronomy and fake news below please ignore me.

          also Pluto lovers should note that orbital dominance takes longer the farther out you are, due to the size of the orbit itself and the sheer amount of time it takes to make a trip around, limiting interactions with neighbors.

          Pluto will eventually own it’s orbit and whatever species has inherited the earth by then may decide to grant it full planet status again!

          • marcos@lemmy.world
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            6 months ago

            and whatever species has inherited the earth by then

            Well, only if we move the Earth safely outwards of the huge Sun.

            • DigitalDruid@lemmy.sdf.org
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              6 months ago

              You made me curious about the timeframe and it turns out I had it completely wrong.

              Pluto’s lack of orbital dominance is a matter of size not time, it’s already had the required time it’s just too wee to get it done. Pluto will never be a full planet!