On the Influence of Pluto on Twotino Dynamics Through Their Mutual 4:3 Mean Motion Resonance

Context: The role of Pluto contributing to the long-term evolution of the trans-Neptunian region has been considered significant only over its neighboring Plutinos. However, it has recently been found that the long-term stability of the Twotino population is strongly affected when including Pluto as a massive object in simulations, while Eris, with a similar mass, has a negligible effect. Aims: We hypothesize that the effect of Pluto on Twotinos results from the latter being trapped in a 4:3 mean motion resonance (MMR) with Pluto. In this work, we aim to demonstrate the resonant behavior of Twotinos within Pluto's 4:3 MMR and the significance of this resonance for the long-term evolution of the population. Methods: We run high-resolution, 10 Myr REBOUND simulations of the observed Twotino population in the Kuiper belt, under the perturbations of the Sun, the four giant planets, and Pluto, as massive objects. Results: We find that all objects trapped in the 2:1 MMR with Neptune are locked in a weak 4:3 MMR with Pluto. The 4:3 resonant angles of most objects trapped in the leading and trailing islands of the 2:1 MMR, librate with amplitudes lower than $360^\circ$. Objects in the symmetric islands of the 2:1 MMR librate in the 4:3 MMR with amplitudes greater than $360^\circ$, but, contrary to circulating objects, will oscillate by up to $840^\circ$ visiting preferred angles on Pluto's co-rotating frame, indicating a diluted resonant effect that may also perturb their orbits on secular timescales. Conclusions: The importance of Pluto in shaping the structure of the trans-Neptunian region should be reconsidered, specifically for resonant populations. Moreover, with current computational power, its exclusion from simulations can not be justified.