Comment

I think “Planet” should be a gravitationally rounded mass that’s not a star anyway. Those can be divided into rocky and gaseous, and further divided by principal composition.

Smaller than that isn’t usually worth having a name, but moons can be just as interesting as free orbiting planets.

The distinction between minor and major planets is decently clear in our star system, but if we define it poorly it won’t help us understand other systems or why the major ones are important. It’s definitely not enough to disqualify minor planets from being full planets though. Go ahead and declare 8 major planets arbitrarily, but don’t try to justify ignoring the other few dozen planetoids poorly.

source

Sort:hotnew top

rockerface@lemmy.cafe ⁨6⁩ ⁨days⁩ ago
That would make Earth-Moon a binary planet. Which I’m cool with, actually.

source
- mnemonicmonkeys@sh.itjust.works ⁨5⁩ ⁨days⁩ ago
  The barycenter of the Earth-Moon system sits well within Earth’s radius. There is no/definition under which the Earth-Moon system is considered binary
  
  source
  - rockerface@lemmy.cafe ⁨5⁩ ⁨days⁩ ago
    The barycentre of Sun-Jupiter system is outside of the Sun half the time. It’s a really bad metric for determining that, as it depends on the distance between two bodies and not just on their relative masses.
    
    source
    mnemonicmonkeys@sh.itjust.works ⁨4⁩ ⁨days⁩ ago
    Except Jupiter is very clearly not a star. It’s an order of magnitude off of the mass required for fusion.
    
    source
    -> View More Comments
mnemonicmonkeys@sh.itjust.works ⁨5⁩ ⁨days⁩ ago

but don’t try to justify ignoring the other few dozen planetoids poorly.

There’s 200+ kuiper belt objects that are large enough to be spherical, and most don’t have names

source
- Tlaloc_Temporal@lemmy.ca ⁨2⁩ ⁨days⁩ ago
  200+ dwarf planet candidates. Lots of them have very low densities, and most are too far away to know hardly anything about them. Pluto was only confirmed to be in hydrostatic equilibrium with New Horizons, and Quaoar has a Dwarf Planet name, but probably isn’t in hydrostatic equilibrium.
  
  It’s not the specific bodies I’m worried about, it’s a useful idea of a planet. Finding dozens or hundreds more of them should be exciting, not a reason to throw up our hands and disqualify them.
  
  source