Disturbances in the Rotational Dynamics of Asteroid (99942) Apophis at its Approach to the Earth in 2029

Abstract—

Using numerical modeling of the rotational dynamics of asteroid (99942) Apophis, the disturbances that occur in the rotational motion of asteroids during their close approaches to the Earth were studied. Such events can lead to significant changes in the speed of the asteroid’s own rotation and the orientation of its rotation axis in space. Assuming that the figure of Apophis is approximated by a triaxial ellipsoid, the dependences of changes in the rotation period of an asteroid on the parameters of the orbit and its rotational state before approaching the Earth were studied. It has been established that the rotation period of Apophis, which is currently about 30 h, may change due to the next approach to Earth in 2029 very significantly—to 10–15 h; in numerical experiments, both acceleration and deceleration of the asteroid’s rotation were observed. Perturbations in the rotational motion of the asteroid noticeably affect its further orbital dynamics as a result of changes in the magnitude of the Yarkovsky effect. It was concluded that as a result of close approach, the average rate of change of the semimajor axis of Apophis’s orbit caused by the Yarkovsky effect, which is currently about 200 m/year, may decrease to 160 m/year or increase to 300 m/year.