I can't seem to get a consistent answer regarding the question of whether or not satellites (moons) of trans-Neptunian objects are considered to be trans-Neptunian objects, given that they do not orbit the sun directly. Any help clarifying this issue would be greatly appreciated.

  • $\begingroup$ How would you phrase that Question if a satellite wasn't a satellite, but a solo object? $\endgroup$ Aug 12, 2021 at 22:43

1 Answer 1


Yes/No as needed.

The MPC, which is fairly authoritative, lists only (134340) Pluto, and doesn't include Charon and the other satellites of Pluto. Formally, binary asteroids are given a single classification, so 2000 CF105 only has a single code, despite being formed of two pieces of ice and rock.

In other contexts it might be convenient to include it. It wouldn't be wrong to include Charon in a discussion of the formation of TNOs.

Nobody really cares enough to try to pass any kind of rule, it is normal and acceptable for context to establish meaning. Language exists to serve us, an not the other way round.

  • 2
    $\begingroup$ Re Nobody really cares enough to try to pass any kind of rule -- Especially not after the immense pushback against the 24 August 2006 decision by the IAU that deemed Pluto not to be a planet. Been there, done that, let's not go through that again. While I do agree with the IAU decision, I also agree with their decision to not go through all that drama again. $\endgroup$ Aug 11, 2021 at 9:55
  • $\begingroup$ Thank you for your answer. ) $\endgroup$ Aug 21, 2021 at 3:29

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