Not a simple relationship between Neptune's migration speed and Kuiper belt inclination excitation
Abstract
We examine the inclination excitation mechanisms for Kuiper belt objects captured into Neptune's 3:2 mean motion resonance and the hot classical belt during Neptune's outward migration. The widely dispersed present day inclination distributions in these populations have been interpreted as strong evidence that Neptune must have migrated slowly because slow migration allows for multiple scattering events to raise the inclinations of Kuiper belt objects. However, in our numerical simulations we find counter-examples that show that the degree of inclination excitation is not necessarily correlated with migration timescale. A deep analysis of the simulations finds that secular excitation of inclinations can play an important role in shaping the final inclination distributions, especially for Neptune's 3:2 resonance which is located very near a strong inclination secular resonance in the Kuiper belt. In the simulations, the relative importance of scattering versus secular excitation depends on the selection of pre-migration initial conditions for the planets and how their eccentricities and inclinations are (made to) evolve during migration; these choices affect the secular architecture of the giant planets as they migrate. The degree of inclination excitation in the post-migration 3:2 and hot classical populations can be very sensitive to the planets' initial conditions and to the simplifications adopted in the numerical model to make the simulations computationally tractable. We suggest that the inclination distribution of the Kuiper belt is not conclusive evidence for a slow migration speed of Neptune and that other lines of evidence are required to constrain migration speed.
- Publication:
-
AAS/Division of Dynamical Astronomy Meeting
- Pub Date:
- June 2019
- Bibcode:
- 2019DDA....5020105V