We measured the mean plane of the Kuiper belt as a function of semi-major axis. For the classical Kuiper belt as a whole (the non-resonant objects in the semi-major axis range 42.48 au), we find a mean plane of inclination im = 1.81°+0.7°--0.4°and longitude of ascending node Ωm = 77°+18°-14°(in the J2000 ecliptic-equinox coordinate system), in accord with theoretical expectations of the secular effects of the known planets. With finer semi-major axis bins, we detect a statistically significant warp in the mean plane near semi-major axes 40.42 au. Linear secular theory predicts a warp near this location due to the v18 nodal secular resonance, however the measured mean plane for the 40.3-42 au semi-major axis bin (just outside the v18) is inclined ∼13° to the predicted plane, a nearly 3-δ discrepancy. For the more distant Kuiper belt objects of semi-major axes in the range 50.80 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 im = 9.1°+6.6°-3.8°and longitude of ascending node Ωm = 227°+18°-44°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 close-in (a ≲ 100 au), unseen small planetary-mass object in the outer solar system is responsible for the warping.
|Original language||English (US)|
|State||Published - Apr 8 2017|
- Celestial Mechanics
- Kuiper Belt: General
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