Comparison of the atmospheric radius for different core masses and headwind parameters. The Hill radius is by definition independent of the headwind parameter. We fit a power law to the data points R_atm/R_Earth = a · (M_c /M_Earth)ⁿ using the relative least-squares method. When the headwind is included, we obtain a = 4.7 ± 0.6, n = 0.67 ± 0.08. Without the headwind, the result of the fit is a = 5.7 ± 0.3, n = 0.62 ± 0.04.