YORP效应机理研究与小行星自转状态演化仿真

YORP effect on the evolution of asteroid spin states

要YORP效应是不规则小行星表面再辐射热量的反冲力对小行星产生净力矩,导致小行星自转状态发生改变的现象.研究YORP效应有助于了解小行星的演化历史、双星系统的形成以及太阳系的起源和发展.从产生机理出发,本文首先建立了结合热物理模型和考虑地貌遮挡作用的YORP效应量化方法,并将该方法用于多面体模型,探究了热惯量对表面温度和反冲力的影响,随后实现了多颗小天体的YORP曲线数值计算和自转状态演化仿真,验证了理论计算的有效性.以上探索对进一步完善YORP效应理论和揭示小行星的结构演化驱动力等具有借鉴意义.

With the rise of the second deep space exploration, more and more attention has been paid to the research of asteroid as well as the YORP effect. The YORP effect, mainly arising from the thermal radiation from an irregularly shaped surface, may cause significant changes in spin rate and obliquity of an asteroid over millions of years. The study of the YORP effect plays an essential role in understanding the evolution of asteroids, the formation of binary systems, and the origin and development of the solar system. There are several methods on the evaluation of the YORP effect based on different models in the existing literature. As applying basic research, this study reviews the theory of the YORP effect, including thermal physical model (TPM), and improves the derivation of the formula. Furthermore, a horizon map is considered to describe the self^shelter, and the magnitude and direction of the radiative recoil force are amended according to the local horizon map. Based on the polyhedral asteroid model, an algorithm is proposed to attain the horizon map, the relationship between the inclination of the asteroid rotation axis and the YORP moment, and to simulate the spin state evolution numerically. Comparisons on numerical calculations and astronomical observation analyses are performed for several simple conditions to validate the performance of the TPM algorithm. Then, using the precise polyhedral shape models derived from radar observations, the YORP moment of many asteroids and its rotation state evolution are investigated. This study will help to reveal the formation and evolution of different asteroid structures and is of considerable significance to the target selection and target physical properties characterization of future asteroid exploration missions.