Best coplanar edge-on orbital evolution shown for 50 kyr from the numerical simulation. Left panel, from top to bottom: orbital evolution of the companions’ semimajor axes, eccentricities, and the secular apsidal angle Δω. Clearly no change in a₁ and a₂ can be seen, while e₁ and e₂ are librating in opposite phase with small amplitudes. Other panels: resonance angles θ_1,2,3 and θ_4,5,6, which are clearly librating around 0° indicating the resonant nature of the system. See text for more details.