A rotating variable is a star that changes in brightness as it spins around, due to variations in brightness on its surface or to a non-spherical shape (see ellipsoidal variable). Irregular surface brightness may be due to the presence of large starspots (see BY Draconis star) or magnetic effects, as in magnetic variables (see Alpha² Canum Venaticorum star and SX Arietis star) or oblique rotators (stars in which the spin axis and magnetic axis are out of alignment).