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Post-instability impact behaviours of compact three planet systems

Presentation #312.05 in the session “Exoplanets and Systems: Orbital Dynamics 3”.

Published onOct 26, 2020
Post-instability impact behaviours of compact three planet systems

A significant number of compact multi-exoplanet systems have been uncovered by recent observational missions. The tight orbital spacing of these systems has led to much effort being applied to the understanding of their stability; however, a key limitation of the majority of these studies is the termination of simulations as soon as the orbits of two planets cross. In this work we explore the stability of compact three planet systems but continue our simulations all the way to the first collision of planets to yield a better understanding of the lifetime of these systems post instability event. Analogues from our own solar system are used throughout in the form of a Sun-like star orbited by three Earth-like secondaries. Integrations are continued until collision or for up to 1 billion orbits for the most stable of systems. We choose the initial semi-major axes equally spaced in units of mutual Hill radii from a value of 3.5–8.3 and perform ~5000 integrations evenly spaced within this range; here, we recover both the time of instability and trends found in previous works but also obtain the survival time of each system after this event. Using the survival time we present the probability over time of an impact between planets once a system becomes unstable and show a dependency between the survival time and the initial orbital spacing. In particular, we find that long survival times are particularly rare in the coplanar case regardless of the choice of initial spacing. Additionally, we also examine the effects of deterministic chaos upon the time to collision and show the effect that the choice of integrator can have upon simulation results. We generalise our results throughout to show both the behaviour of systems with an inner planet initially located at 1 AU and 0.25 AU.

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