活动小行星311P/PANSTARRS的动力学lk 特性分析

311P/PANSTARRS是一颗活动小行星, 具有小行星和彗星的双重特征, 是中国``天问二号''的探测目标之一. 311P/PANSTARRS直径较小, 约为400 m, 非引力效应可能会对其长期动力学演化产生较大的影响. 通过假定不同表面组分, 研究了Yarkovsky效应对311P/PANSTARRS轨道演化的影响, 讨论了密近交汇、 非破坏性碰撞和YORP (Yarkovsky-O''Keefe-Radzievskii-Paddack)效应等非引力效应, 计算了小行星与大行星密近交汇及碰撞概率, 估计了311P/PANSTARRS达到自转周期分裂极限的时标. 模拟结果显示与纯引力模型相比, Yarkovsky效应可能会加快311P/PANSTARRS离开当前共振区域, 大约在10Myr以后311P/PANSTARRS会离开当前所在共振带, 在表面覆盖风化层的情况下有机会通过v6长期共振成为越火小行星; 在考虑YORP效应的情况下, 311P/PANSTARRS在2 Myr时标内可达到自转周期分裂极限; 在考虑Yarkovsky效应及YORP效应等因素的情况下, 311P/PANSTARRS在10 Myr时标内仍可保持其动力学稳定性, 且YORP效应不会显著影响其半长径偏移量.

Dynamical Characteristics of Active Asteroid 311P/PANSTARRS

Active asteroids have received lots of attention since they were discovered. 311P/PANSTARRS is one of the most interesting active asteroids in China recently and one of the targets of Tianwen-2. Because of its small size of about 400m, the Yarkovsky effect may have a significantly influence on its long-term dynamics. This paper discussed the changes in the long-term motion of 311P/PANSTARRS caused by the Yarkovsky effect. By assuming different surface compositions, this simulation introduced the semi-major axis drift by propagating orbits of orbital clones, and the effects of other factors such as close encounters, meteoroid impacts and YORP effect on the orbit evolution of 311P/PANSTARRS were also discussed. Additionally, we estimated the time scale for 311P/PANSTARRS to reach its rotation period of splitting limit. The results of the simulations show that the Yarkovsky effect may cause 311P/PANSTARRS to exit from the resonance region faster when compared to a purely gravitational model. 311P/PANSTARRS will leave the current resonance region after roughly 10Myr and have a chance to become a Mars-crossing asteroid through v6 secular resonance due to the diurnal Yarkovsky effect if its surface is covered by a regolith layer. It is concluded that 311P/PANSTARRS is stable at least 10 Myr time scale even if taking the Yarkovsky effect and the YORP effect into account. Furthermore, the YORP effect may not significantly affect the semi-major axis drift of 311P/PANSTARRS.