Heliocentric distance r versus time t for all four embryos in the simulation shown in Fig. 4. The black triangles correspond to the time of individual snapshots. There is an output from the full hydrodynamic simulation (lines), and an N-body simulation with no discs and no torques (points) for comparison. The latter was restarted from the very same initial conditions, at t = 2605 P_orb. One can see the merger event at t ≐ 2609 P_orb. In the case of the N-body simulation, the evolution is different, because without the disc torques the trajectories are mostly Keplerian, the encounter between embryos 3 and 4 just one orbit prior to the merger (2+4) has a different geometry, so the merger actually does not occur.