Demonstration of the sensitivity of the model to the Q_p parameter. Top panel: The final rotation period vs. Q_p parameter. Each dot in this plot corresponds to the Q_p and the final Eris rotation period, P_pf, of a specific run. All other model parameters were kept the same. Bottom panel: Evolution of the rotation period of Eris, using the models presented in the upper panel. The colours of the curves correspond to the colour of the symbols on the upper panel, the red curve is the evolution of the orbital period.