Surface density snapshot of our single-planet, gas-rich simulation (model 2) at 3500 years. Green dashed circles are at 0.5, 1, and 1.5 au. The blue dot indicates the planet’s position. This snapshot is taken near the time of the planet–vortex close encounter. The vortex, of approximate mass 100 M_⊕, is seen at around 1.1 au. After the encounter, the planet is perturbed radially inward (Figure 1). The vortex ultimately decays away (Figure 4).