Initial conditions from Agnor & Hamilton (2006, Nature 441, 192–194): an equal-mass Triton binary on a planar encounter with v∞ = 0.50 km s⁻¹, q_e = 8 R_N, and a_B = 20 R₁ (ρ₁ = 2.0 g cm⁻³). The encounter is set up in a Neptune-centered frame, as in the paper's Figure 1 — the Sun is included for context at ~30 AU. A binary orbital phase that yields exchange capture is used: one member of the binary is transferred to Neptune while the other is ejected. Binary exchange capture is the leading explanation for Triton's retrograde orbit and is thought to have occurred early in Solar System history when Neptune still had a massive protoplanetary disk.