Illustration of the light sails in the one-facet illumination state and two-facet illumination (left panels) and their light curves (right panels). The rotation angular momentum is J, and the spin vector is along the major principal axis, z. The position vector r is pointing ‘Oumuamua away from the Sun. The solid lines denote the absolute magnitude, while the dashed line denotes the areas of projection along the sunlight direction. The imperfect consistency results from the nonzero phase angle ~20° (Fraser et al. 2018).