List of Minor-planet Groups - Groups at Or Beyond The Orbit of Neptune

Groups At or Beyond The Orbit of Neptune

• The Neptune trojans currently consist of eight objects. The first one to be discovered was 2001 QR₃₂₂.
• Trans-Neptunian objects (TNOs) are anything with a mean orbital radius greater than 30 AU. This classification includes the Kuiper-belt objects (KBOs), the scattered disc, and the Oort cloud.
  • Kuiper-belt objects extend from roughly 30 AU to 50 AU and are broken into the following subcategories:
    • resonant objects occupy orbital resonances with Neptune the 1:1 resonance of the Neptune trojans.
      • Plutinos are by far the most common resonant KBOs and are in a 2:3 resonance with Neptune, just like Pluto. The perihelion of such an object tends to be close to Neptune's orbit (much as happens with Pluto), but when the object comes to perihelion, Neptune alternates between being 90 degrees ahead of and 90 degrees behind of the object, so there's no chance of a collision. The MPC defines any object with a mean orbital radius between 39 AU and 40.5 AU to be a plutino. 90482 Orcus and 28978 Ixion are among the brightest known.
      • Other resonances. There are several known objects in the 1:2 resonance, dubbed twotinos, with a mean orbital radius of 47.7 AU and an eccentricity of 0.37. There are several objects in the 2:5 (mean orbital radius of 55 AU), 4:7, 4:5, 3:10, 3:5, and 3:4 resonances, among others. The largest in the 2:5 resonance is 2002 TC₃₀₂, and the largest in the 3:10 resonance is 2007 OR₁₀
    • Classical Kuiper-belt objects, also known as cubewanos (after (15760) 1992 QB₁), have a mean orbital radius between approximately 40.5 AU and 47 AU. Cubewanos are objects in the Kuiper belt that didn't get scattered and didn't get locked into a resonance with Neptune. The largest is Makemake.
  • Scattered disc objects (SDOs) typically have, unlike cubewanos and resonant objects, high-inclination, high-eccentricity orbits with perihelia that are still not too far from Neptune's orbit. They are assumed to be objects that encountered Neptune and were "scattered" out of their originally more circular orbits close to the ecliptic. The most massive known dwarf planet, Eris, belongs to this category.
    • Detached objects (extended scattered disk) with generally highly elliptical, very large orbits of up to a few hundred AU and a perihelion too far away from Neptune for any significant interaction to occur. The most famous in this class is Sedna. A more typical member of the extended disk is 2000 CR₁₀₅
  • The Oort cloud is a hypothetical cloud of comets with a mean orbital radius between approximately 50,000 AU and 100,000 AU. No Oort-cloud objects have been detected, the existence of this classification is only inferred from indirect evidence. Some astronomers have tentatively associated 90377 Sedna with the Oort cloud.