近地小行星的热惯性和对Yarkovsky效应大小的影响
Thermal inertia of near-Earth asteroids and implications for the magnitude of the Yarkovsky effect
摘要：
热惯性决定了小行星表面的温度分布，因此也决定了雅科夫斯基效应的大小。后者导致公里大小的小行星轨道逐渐漂移，并在近地小行星从主带脱离和小行星家族动态扩散方面发挥重要作用。目前，人们对千米大小的小行星的热惯性知之甚少。在这里，我们表明，平均热惯性的样品的NEAs在公里大小的范围是200 $\pm$ 40焦耳米2秒0.5 K-1。此外，我们确定了一个趋势，增加的热惯性与小行星直径，D。这表明，轨道半长轴的漂移率对小行星大小的依赖性，由于雅科夫斯基效应，是一个比通常采用的D^（1）依赖性更为复杂的函数，而且，由雅科夫斯基驱动的轨道迁移率射入近地小行星源区的物体的大小分布，向较小大小的倾斜程度比通常假设的要小。我们将讨论这一事实如何有助于解释千米大小的近地小行星和主带小行星大小分布斜率的微小差异。
英文摘要：
Thermal inertia determines the temperature distribution over the surface of an asteroid and therefore governs the magnitude the Yarkovsky effect. The latter causes gradual drifting of the orbits of km-sized asteroids and plays an important role in the delivery of near-Earth asteroids (NEAs) from the main belt and in the dynamical spreading of asteroid families. At present, very little is known about the thermal inertia of asteroids in the km size range. Here we show that the average thermal inertia of a sample of NEAs in the km-size range is 200 $\pm$ 40 J m−2 s−0.5 K−1. Furthermore, we identify a trend of increasing thermal inertia with decreasing asteroid diameter, D. This indicates that the dependence of the drift rate of the orbital semimajor axis on the size of asteroids due to the Yarkovsky effect is a more complex function than the generally adopted D^(−1) dependence, and that the size distribution of objects injected by Yarkovsky-driven orbital mobility into the NEA source regions is less skewed to smaller sizes than generally assumed. We discuss how this fact may help to explain the small difference in the slope of the size distribution of km-sized NEAs and main-belt asteroids.
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