For any object rotating about a rotational axis, the conservation of angular momentum holds if no external torque acts on it. For example, suppose the Sun, having an angular velocity of two point six times ten to the power of negative six radians-per-second, collapses into a white dwarf such that its radius decreases by a factor of five hundred. Assuming that the lost mass carries away no angular momentum, what will be the white dwarf's final rotational kinetic energy? Here the known quantities are initial and final radii, initial and final masses, and the angular velocity of the Sun. The unknown quantity is the final rotational kinetic energy of the white dwarf. Here, the conservation of angular momentum holds, and assuming that the Sun and the white dwarf each have uniform spherical densities, substituting for their moment of inertia, the final angular velocity of the white dwarf can be calculated. The rotational kinetic energy of the white dwarf can be calculated by substituting the value of the final angular velocity.