this post was submitted on 28 Jun 2024
1706 points (98.2% liked)

People Twitter

5390 readers
2025 users here now

People tweeting stuff. We allow tweets from anyone.

RULES:

  1. Mark NSFW content.
  2. No doxxing people.
  3. Must be a tweet or similar
  4. No bullying or international politcs
  5. Be excellent to each other.
  6. Provide an archived link to the tweet (or similar) being shown if it's a major figure or a politician.

founded 2 years ago
MODERATORS
 
you are viewing a single comment's thread
view the rest of the comments
[–] [email protected] 8 points 5 months ago (2 children)

The issue is, as I understand it, we either have 8 planets (or 9, if there is an exoplanet), or a whole bunch of planets, depending on how narrowly we define them.

[–] [email protected] 7 points 5 months ago (1 children)

Yeah this is the correct take. Either Pluto (and by extension, any object of similar size) is a planet, which would mean there's thousands of Pluto-sized planets in the solar system; or pluto is 'too small' to be a planet. Which is the answer they (Sci community) settled on, because if every comet/asteroid is within the threshold definition of 'planet' then there would be no point in distinguishing planets at all.

Kinda like how we have dwarf-stars and supermassive stars 1000x bigger than our sun. If they were all the same size there would be no point defining them beyond 'star'.

[–] [email protected] 6 points 5 months ago* (last edited 5 months ago)

Pluto being too small isn't actually the grounds on which it got demoted. The size requirement is just being massive enough to reach hydrostatic equilibrium - that is, be heavy enough that it's round. Pluto does meet this one

The one it fails is clearing its orbit. This basically means being much heavier than everything else in the same orbit. Be gravitationally in charge of your orbit. The other eight are all hundreds if not thousands of times heavier than everything else in their orbit (not including moons, since they're gravitationally bound to the planet anyway), whereas Pluto is less than a tenth of the total mass in its own orbit. Ceres is actually more gravitationally dominant over its orbit than that, although still nowhere near the eight planets.

This one sounds a bit weird at first, but I kinda like how it has such a massive delineation between the things we instinctively think of as planets and everything else.

[–] [email protected] 2 points 5 months ago

It's also the fact that Pluto doesn't have its own orbital slot. It is clearly something that escaped Uranus at some point, that's why their orbits intersect. A planet doesn't just have to have a certain size, it also has to have its own distinct orbital path.