Dynamical Analysis of Three Distant Trans-Neptunian Objects with Similar Orbits

This paper reports the discovery and orbital characterization of two extreme trans-Neptunian objects (ETNOs), 2016 QV89 and 2016 QU89, which have orbits that appear similar to that of a previously known object, 2013 UH15. All three ETNOs have semimajor axes a ≈ 172 au and eccentricities e ≈ 0.77. The angular elements (i, ω, Ω) vary by 6°, 15°, and 49°, respectively, between the three objects. The two new objects add to the small number of TNOs currently known to have semimajor axes between 150 and 250 au, and they serve as an interesting dynamical laboratory to study the outer realm of our solar system. Using a large ensemble of numerical integrations, we find that the orbits are expected to reside in close proximity in the (a, e) phase plane for roughly 100 Myr before diffusing to more separated values. We find that an explanation for the orbital configuration of the bodies as a collision product is disfavored. We then explore other scenarios that could influence their orbits. With aphelion distances over 300 au, the orbits of these ETNOs extend far beyond the classical Kuiper Belt and an order of magnitude beyond Neptune. As a result, their orbital dynamics can be affected by the proposed new solar system member, referred to as Planet Nine in this work. With perihelion distances of 35–40 au, these orbits are also influenced by resonant interactions with Neptune. A full assessment of any possible new solar system planets must thus take into account this emerging class of TNOs.