Dynamical impact of the Planet Nine scenario: N-body experiments

TL;DR

This study uses N-body simulations to explore how a hypothetical Planet Nine could influence the orbits of extreme trans-Neptunian objects, revealing potential stability or instability over hundreds of millions of years.

Contribution

It provides detailed numerical experiments on Planet Nine's dynamical effects, refining constraints on its possible orbit based on orbital stability of ETNOs.

Findings

Planet Nine can stabilize some ETNOs like Sedna for hundreds of Myr.

Certain ETNOs become unstable and ejected within tens of Myr under some Planet Nine scenarios.

Slight modifications to Planet Nine's orbit improve the long-term stability of ETNOs.

Abstract

The Planet Nine hypothesis has now enough constraints to deserve further attention in the form of detailed numerical experiments. The results of such studies can help us improve our understanding of the dynamical effects of such a hypothetical object on the extreme trans-Neptunian objects or ETNOs and perhaps provide additional constraints on the orbit of Planet Nine itself. Here, we present the results of direct N-body calculations including the latest data available on the Planet Nine conjecture. The present-day orbits of the six ETNOs originally linked to the hypothesis are evolved backwards in time and into the future under some plausible incarnations of the hypothesis to investigate if the values of several orbital elements, including the argument of perihelion, remain confined to relatively narrow ranges. We find that a nominal Planet Nine can keep the orbits of (90377) Sedna and 2012 VP113 relatively well confined in orbital parameter space for hundreds of Myr, but it may make the orbits of 2004 VN112, 2007 TG422 and 2013 RF98 very unstable on time-scales of dozens of Myr, turning them retrograde and eventually triggering their ejection from the Solar system. Far more stable orbital evolution is found with slightly modified orbits for Planet Nine.