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Pluto is still a planet, just a dwarf one (thelemmy.club)
submitted 1 month ago* (last edited 1 month ago) by to c/historymemes@piefed.social
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[–] 3 points 1 month ago (1 child)

That's just for our own solar system.

The draft proposal for the definition of a planet was debated vigorously by astronomers at the 2006 IAU General Assembly, and a new version slowly took shape. This new version was more acceptable to the majority and was presented to the members of the IAU for a vote at the Closing Ceremony of the General Assembly. By the end of the Prague General Assembly, IAU members voted that the definition of a planet in the Solar System would be as follows: "A celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit. (p. 1)" More generally, a planet: a) orbits its host star, just as the Earth and Jupiter orbit the Sun, b) is large enough to be mostly round, and c) must have an important influence on the orbital stability of the other objects in its neighbourhood.

https://www.iau.org/IAU/Science/What-we-do/Pluto-and-the-Developing-Landscape-of-Our-Solar-System.aspx

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  • [–] 2 points 1 month ago (1 child)

    The IAU resolution (pdf) that they voted on does not include what comes after "More generally". The page that you link to is apparently the source and is not official.

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  • [–] 4 points 1 month ago (1 child)

    That PDF says "Definition of a Planet in the Solar System" and "The IAU therefore resolves that planets and other bodies in our Solar System be defined into three distinct categories in the following way".

    I mean, what would you call the big, roughly ball-shaped thingies orbiting Kepler-62?

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  • [–] 1 point 1 month ago (2 children)

    Because planets only exist in the solar system.

    They attempted to create a definition for an "exoplanet" but that never passed, so aggregations of matter orbiting stars outside the solar system have no official name.

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  • [–] 3 points 1 month ago

    I feel quite confident that we, as a species, will one day, in the not too distant future (maybe even next Sunday CE), come collectively to the conclusion that things that behave like the planets of our solar system but do so with regards to a different star also deserve the honour of being called planets. That's the least bit of faith I have in humanity.

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