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Title: A Dynamical Systems Approach to the Theory of Circumbinary Orbits in the Circular Restricted Problem

To better understand the orbital dynamics of exoplanets around close binary stars, i.e., circumbinary planets (CBPs), we applied techniques from dynamical systems theory to a physically motivated set of solutions in the Circular Restricted Three-Body Problem (CR3BP). We applied Floquet theory to characterize the linear dynamical behavior—static, oscillatory, or exponential—surrounding planar circumbinary periodic trajectories (limit cycles). We computed prograde and retrograde limit cycles and analyzed their geometries, stability bifurcations, and dynamical structures. Orbit and stability calculations are exact computations in the CR3BP and reproducible through the open-source Python packagepyraa. The periodic trajectories ( produce a set of noncrossing, dynamically cool circumbinary orbits conducive to planetesimal growth. For mass ratiosμ∈ [0.01, 0.50], we found recurring features in the prograde families. These features include (1) an innermost near-circular trajectory, inside which solutions have resonant geometries, (2) an innermost stable trajectory (ac≈ 1.61 − 1.85abin) characterized by a tangent bifurcating limit cycle, and (3) a region of dynamical instability (a≈ 2.1abin; Δa≈ 0.1abin), the exclusion zone, bounded by a pair of critically stable trajectories bifurcating limit cycles. The exterior boundary of the exclusion zone is consistent with prior determinations ofacaround a circular binary. We validate our analytic results withN-body simulations and apply more » them to the Pluto–Charon system. The absence of detected CBPs in the inner stable region, between the prograde exclusion zone andac, suggests that the exclusion zone may inhibit the inward migration of CBPs.

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Publication Date:
Journal Name:
The Astronomical Journal
Page Range or eLocation-ID:
Article No. 140
DOI PREFIX: 10.3847
Sponsoring Org:
National Science Foundation
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