Secular change in the spin states of asteroids due to radiation and gravitation torques. New detections and updates of the YORP effect

Vol. 682
10. Planets and planetary systems

Secular change in the spin states of asteroids due to radiation and gravitation torques. New detections and updates of the YORP effect

The motion of near-Earth asteroids is significantly influenced by non-gravitational forces, specifically thermal torques resulting from the proximity to the Sun. These effects are known as the Yarkovsky effect for orbital dynamics and the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect when impacting the object's rotation. The latter effect is stronger when the object's shape is irregular, a common characteristic of small bodies. Detecting the YORP effect involves identifying a secular acceleration in rotation, a phenomenon that has been observed in fewer than ten objects. In this study, the authors detect the YORP effect in two new asteroids, refine measurements for two others, and highlight an asteroid that exhibits a deceleration in rotation, the opposite of what is usually seen. To achieve this, they analyzed the light curves of these objects, obtained through photometric observations from various observatories. Since these light curves depend on the rotation and shape of the objects, their analysis requires combining rotational and shape models. These new data could mark a significant advancement in our understanding of the YORP effect, which remains largely unconstrained.