Evolution of the positions of Uranus and Neptune. The horizontal |and vertical axes represent the a_N and a_U, respectively. The color of the points indicates the migration rate of Uranus at each position. The orange dots denote the initial a_N and a_U in each set of simulations. The points with black borders represent hypothetical extensions of the real Solar System’s migration, while the dotted black line shows the linear fit of these points with black borders. The hollow circles mark the positions where a_U reaches its minimum value, and the solid black line represents the linear fit of all black circles. The dashed black line indicates the location corresponding to the R_2N:1U.