All the trans-Neptunian object's orbits I know are very inclined compared to those of the eight recognized planets, and Centaur's orbits are highly inclined as well.

Are there any known Centaurs and/or trans-Neptunian objects or TNOs whose orbit isn't significantly inclined to the ecliptic or to the invariable plane, but is on about the same plane as the eight main planets?

And to double check, the hypothetical planet Nine also has a high orbital inclination, doesn't it?

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    $\begingroup$ Yes, classical KPOs or cubewanos typically have low inclination and low eccentricities. Also, see this picture: imgur.com/Z0ynCFj $\endgroup$ – Nilay Ghosh Nov 13 '20 at 14:17
  • $\begingroup$ @NilayGhosh I'd upvote your comment if I could. There really are some examples that have a very low inclination and some that (as I knew already like in case of Makemake) have a very high inclination. $\endgroup$ – John Nov 13 '20 at 14:48

Queries to the JPL Small Body Database or the ESA Asteroids Dynamic Site for such bodies return several results. Some of the bigger ones are:

Centaurs with H < 10 and i < 4°

TNOs with H < 5 and i < 2°

  • $\begingroup$ Thank you. I was looking especially for named objects, but Mr. Ghosh's Wikipedia link provides some: Albion, Arrokoth (Ultima Thule) and Logos. Since Arrokoth and Logos are (contact-)binary objects, especially the celestial body Albion is the kind of object I was looking for. $\endgroup$ – John Nov 14 '20 at 6:22
  • $\begingroup$ @John Relaxing the search criteria above yields Centaurs Hylonome and Echeclus and TNOs Sila-Nunam and Praamzius among others. $\endgroup$ – Mike G Nov 14 '20 at 14:13
  • $\begingroup$ Thank you again. All of them are pretty small, especially the two Centaurs, but their inclination is similar to that of the 8 planets, so why do you say relaxed search criteria? Planet Mercury has an inclination of 7.01° to the ecliptic, we may consider that the upper border, and all the four bodies are within. $\endgroup$ – John Nov 14 '20 at 14:59
  • $\begingroup$ @John The larger H and i you allow, the more objects you include. Any such choice is arbitrary. :) $\endgroup$ – Mike G Nov 14 '20 at 15:31
  • $\begingroup$ One of them has an inclination of less than 2°. H is not important, rather their size and mass. $\endgroup$ – John Nov 14 '20 at 17:00

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