this post was submitted on 08 Jun 2026
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How many planets are in orbit around the sun? 8
How many planets are in the entire universe? 8, because a planet has to orbit the sun.
How many planets have ever completed an orbit around the sun: 8, since Pluto has such a long orbital period that in its entire time as a planet it did not even finish a single one.
Pluto has completed millions of orbits around the sun.
At the time of the IAUs release of the definition of a planet, Neptune had not completed an orbit since its discovery, and yet they still called it a planet. Clearly, this weird and arbitrary statement that you have put forth did not matter.
I think it was sufficiently clear to just be a fun fact, not the implication that pluto did not complete orbits around the sun before it was discovered or whatever
Neptune has completed one though. So Pluto is the only planet to officially not complete an orbit while it was called a planet. It doesn't affect whether it's a planet or not, it's just an interesting quiz question.
That's just for our own solar system.
https://www.iau.org/IAU/Science/What-we-do/Pluto-and-the-Developing-Landscape-of-Our-Solar-System.aspx
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.
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?
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.
Uranus is an aggregation of matter.
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.