Dependence of ∆a(For Ast1) on the binary asteroid’s total orbit. Panel a shows the result of our grid simulation, where the size of Ast1 is 100 km, μ = 0.99 and the semi-major axis of the relative orbit is 2000 km. The x-axis is the periastron distance of the binary’s total orbit, and the y-axis is the change in semi-major axis (Ast1) which is presented in log scale. The different colors mean the different semi-major axis of the binaries’ total orbit. The dots have been shifted horizontally by a small but random amount for better visibility. Panel b shows the relationship between a_tot − a₁ and a_tot. The blue line comes from Eq. (7). The red dots are the mean value of our grid simulation and the error here is the standard deviation.