Apophis: Complex rotation and hazard assessment

We present an updated hazard assessment for near-Earth asteroid (99942) Apophis. The stiff dynamics and the high precision of the trajectory of Apophis call for the most accurate dynamical model. In particular, the dominant source of ephemeris prediction uncertainty is the Yarkovsky effect. We include the Yarkovsky perturbation in the force model by numerically computing the related thermal recoil accelerations. These acceleration are statistically computed according to the known physical properties of Apophis and their uncertainties. Special effort is required to account for the non-principal axis rotation state of Apophis. Finally, we generated Monte Carlo samples to capture the uncertainty in both the orbital elements and the Yarkovsky accelerations and compute the probability of future Earth impacts. Whereas collisions with Earth before 2060 are ruled out, impacts are still possible starting in 2060. The highest impact probability is seven in a million for the April 2068 Earth encounter.