双小行星中的BYORP与耗散：来自DART的启示
BYORP and Dissipation in Binary Asteroids: Lessons from DART
AI总结：
基于DART任务数据，本研究提出双小行星BYORP效应和潮汐耗散新范式，发现球状碎屑天体的BYORP效应较弱且依赖尺寸，能量耗散由短暂大规模材料运动主导。
摘要：
近地双小行星Didymos是2022年9月行星防御演示任务DART的目标。较小的双星组件Dimorphos被航天器撞击，以测量动能撞击进入碎石堆时的动量传递。DART及相关的地基观测活动提供了大量关于Didymos-Dimorphos双星的科学数据。DART揭示了撞击前Dimorphos呈明显的扁球体和椭球形状，而撞击后的观测表明Dimorphos现在具有长球体形状。在此，我们将这些数据点添加到小双小行星的已知属性中，并提出关于辐射双星YORP（BYORP）效应以及小双星中潮汐耗散的新范式。我们发现，像Dimorphos这样由小碎片组成的相对球状天体，其经历的BYORP效应可能比以前认为的要弱，并且更依赖于尺寸。这可以解释几个特征明确的双星中观测到的周期漂移值。我们还提出，小双星中的能量耗散主要由（可能是表面的）材料大规模运动的相对短暂事件主导，而不是长期稳态潮汐耗散。我们提出，DART撞击在Dimorphos上触发了这样一个事件。根据这种高耗散状态的持续时间，Dimorphos可能会在Hera任务到达时比撞击后几周内更加动态松弛。
英文摘要：
The Near-Earth binary asteroid Didymos was the target of a planetary defense demonstration mission DART in September 2022. The smaller binary component, Dimorphos, was impacted by the spacecraft in order to measure momentum transfer in kinetic impacts into rubble piles. DART and associated Earth-based observation campaigns have provided a wealth of scientific data on the Didymos-Dimorphos binary. DART revealed a largely oblate and ellipsoidal shape of Dimorphos before the impact, while the post-impact observations suggest that Dimorphos now has a prolate shape. Here we add those data points to the known properties of small binary asteroids and propose new paradigms of the radiative binary YORP (BYORP) effect as well as tidal dissipation in small binaries. We find that relatively spheroidal bodies like Dimorphos made of small debris may experience a weaker and more size-dependent BYORP effect than previously thought. This could explain the observed values of period drift in several well-characterized binaries. We also propose that energy dissipation in small binaries is dominated by relatively brief episodes of large-scale movement of (likely surface) materials, rather than long-term steady-state tidal dissipation. We propose that one such episode was triggered on Dimorphos by the DART impact. Depending on the longevity of this high-dissipation regime, it is possible that Dimorphos will be more dynamically relaxed in time for the Hera mission than it was in the weeks following the impact.
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