3 ms·

Titan as well.

• adrian_b 2y ago
  By size, the Solar System has 4 Mercury-sized bodies: Mercury, Ganymede and Callisto (the 2 bigger of the 4 big satellites of Jupiter), and Titan (satellite of Saturn). There are also 4 Moon-sized bodies: the Moon, Io and Europa (the 2 smaller of the 4 big satellites of Jupiter), and Triton (satellite of Neptune). Pluto is smaller than Triton, but not much smaller. It is the next in size after these bodies and it could be considered to belong to the same size class as the Moon-sized bodies, because the next smaller bodies are significantly smaller. While Pluto is not a satellite of Neptune, like the satellites it does not have an independent movement, but one that is connected to the movement of Neptune through an orbital resonance.
  • npongratz 2y ago
    The Neptune-Pluto gravitational resonance is pretty neat. Wikipedia has a nice listing of other orbital resonances in the solar system: Likely gravitional: https://en.wikipedia.org/wiki/Orbital_resonance#Mean-motion_resonances_in_the_Solar_System https://en.wikipedia.org/wiki/Orbital_resonance#Mean-motion_... Likely coincidental: https://en.wikipedia.org/wiki/Orbital_resonance#Coincidental_%27near%27_ratios_of_mean_motion https://en.wikipedia.org/wiki/Orbital_resonance#Coincidental...
  • Figs 2y ago
    Eris is slightly smaller than Pluto in volume -- but more massive; it might also be worth considering in that same class.
    • adrian_b 2y ago
      You are right, Eris is close enough in size to Pluto and to the other 4 Moon-sized objects to be considered in the same class size. In the past, for a long time the uncertainties about the sizes of Pluto and of Eris were great, so it was not clear how close in size they are to the other much better known Moon-sized bodies.