Orbital parameters of Kuiper Belt objects

For the classical Kuiper Belt as a whole (the nonresonant objects in the semimajor axis range 42-48au), we find a mean plane of inclination i_m_=1.8{deg}_-0.4{deg}_^+0.7{deg}^ and longitude of ascending node {Omega}_m_=77{deg}_-14{deg}_^+18{deg}^ (in the J2000 ecliptic-equinox coordinate system), in accord with theoretical expectations of the secular effects of the known planets.

With finer semimajor axis bins, we detect a statistically significant warp in the mean plane near semimajor axes 40-42au. Linear secular theory predicts a warp near this location due to the {nu}_18_ nodal secular resonance; however, the measured mean plane for the 40.3-42au semimajor axis bin (just outside the {nu}_18_) is inclined ~13{deg} to the predicted plane, a nearly 3{sigma} discrepancy. For the more distant Kuiper Belt objects of semimajor axes in the range 50-80au, the expected mean plane is close to the invariable plane of the solar system, but the measured mean plane deviates greatly from this: it has inclination i_m_=9.1{deg}_-3.8{deg}_^+6.6{deg}^ and longitude of ascending node {Omega}_m_=227{deg}_-44{deg}_^+18{deg}^.