Presentation #501.04 in the session “KBOs and Multiples”.
A small fraction of dynamically cold Kuiper Belt binaries have near equal mass and have very wide separations. Binaries like this are extremely sensitive to perturbation, the widest of which (2001 QW322 a/RH ≃ 0.22) is so loosely bound that it is unlikely to have survived even 1 billion years in the Kuiper Belt. We use numerical simulations to study the dynamic stability of KBO binaries as well as their evolution as a result of close encounters with other KBO bodies over the history of the solar system. Our integrator is the RMVS4 Swift subroutine which simulates our test binary system and the gravitational impulse of KBO flybys. The system’s initial separations range from 0.03 Hill Radii to 0.23 Hill Radii. To accurately simulate close encounters, we construct velocity and mass distributions for the relevant Kuiper Belt populations that would encounter such a binary, as well as the encounter rate of each population. Due to uncertainties in the mass distributions of the KBO populations, we vary its SFD and its exact density. Our results to date indicate that tighter binaries often widen over time and can form transient ultra-wide binaries. We have also found it unlikely for most ultra wide binaries to survive in the Kuiper Belt for the duration of the solar system. These effects are magnified in simulations where the interacting Kuiper Belt Objects have higher density.