Possible secular trajectories for the HD 74156 system seen in the (ϕ,e₁) plane for I = 0° (top) and in the (ω₁,e₁) plane for I = 35° (bottom). All trajectories are compatible with the current knowledge for this system (Table 1). We show the trajectories using the octupolar approximation (blue) and direct numerical simulations (red). In a) the blue path corresponds to the level curves of constant energy for coplanar orbits. The dot marks the present position of the planet. In b) we additionally show the trajectories using the quadrupolar approximation (green), which corresponds to the level curves of constant energy.