The Curiously Warped Mean Plane of the Kuiper Belt
Abstract
We measured the mean plane of the Kuiper Belt as a function of semimajor axis. For the classical Kuiper Belt as a whole (the nonresonant objects in the semimajor axis range 4248 au), we find a mean plane of inclination {I}_{m}=1\buildrel{\circ}\over{.} {8}_{0\buildrel{\circ}\over{.} 4}^{+0\buildrel{\circ}\over{.} 7} and longitude of ascending node {{{Ω }}}_{m}=77{^\circ }_{{14}^{^\circ }}^{+{18}^{^\circ }} (in the J2000 eclipticequinox 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 4042 au. Linear secular theory predicts a warp near this location due to the {ν }_{18} nodal secular resonance; however, the measured mean plane for the 40.342 au semimajor axis bin (just outside the {ν }_{18}) is inclined ∼ 13^\circ to the predicted plane, a nearly 3σ discrepancy. For the more distant Kuiper Belt objects of semimajor axes in the range 5080 au, 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\buildrel{\circ}\over{.} {1}_{3\buildrel{\circ}\over{.} 8}^{+6\buildrel{\circ}\over{.} 6} and longitude of ascending node {{{Ω }}}_{m}=227{^\circ }_{{44}^{^\circ }}^{+{18}^{^\circ }}. We estimate this deviation from the expected mean plane to be statistically significant at the ∼97%99% confidence level. We discuss several possible explanations for this deviation, including the possibility that a relatively closein (a≲ 100 au), unseen, small planetarymass object in the outer solar system is responsible for the warping.
 Publication:

The Astronomical Journal
 Pub Date:
 August 2017
 DOI:
 10.3847/15383881/aa79ff
 arXiv:
 arXiv:1704.02444
 Bibcode:
 2017AJ....154...62V
 Keywords:

 celestial mechanics;
 Kuiper belt: general;
 Astrophysics  Earth and Planetary Astrophysics
 EPrint:
 This version corrects an error in Figure 7 and typographical errors in some equations in Appendix D (changes accepted as an erratum in AJ)