Trajectories of two moons captured by Neptune and of the ice giant (IG) during the encounter of the two planets. Neptune is the black dot at the origin. The grey line represents the path of the IG at q_enc = 0.003 au, red that of a retrograde circularisable (by tides only) moon [CM (T,R)], and green that of a prograde irregular moon [IM (P)]. Both moons are initially orbiting the IG, entering the plotted area from the bottom left, and then captured by Neptune. The projections onto the x-y plane (dotted lines) are also shown with a zoomed-in view in the top left corner of the plot where the dots show the positions of the objects at the closest approach of the two planets and the arrows the directions of motion.