小行星族的形状分布--小撞击驱动演化的证据
The shape distribution of asteroid families -- evidence for evolution driven by small impacts
摘要：
对小行星亮度变化的统计分析揭示了它们的形状是如何从细长到粗糙的球状形态演变的，这可能是由与撞击有关的现象驱动的。根据斯隆数字巡天移动物体目录，我们确定了11，735颗小行星的形状分布，特别强调了8个突出的小行星家族。在年轻的小行星家族中，小行星有着广泛的形状拉长，这意味着碎片形成。在更古老的家族中，我们看到越来越多的粗糙球体，这与撞击驱动进化的预测一致。古老的家族还包含一组适度拉长的成员，我们认为这对应于更高密度，更耐冲击的前碎片小行星的核心，经历了缓慢的形状侵蚀。百分之几的小行星具有非常细长的形状，可以是年轻的碎片或潮汐重塑的物体。我们的研究结果证实，大多数小行星都被重力束缚在“瓦砾堆”中。
英文摘要：
A statistical analysis of brightness variability of asteroids reveals how their shapes evolve from elongated to rough spheroidal forms, presumably driven by impact-related phenomena. Based on the Sloan Digital Sky Survey Moving Object Catalog, we determined the shape distribution of 11,735 asteroids, with special emphasis on eight prominent asteroid families. In young families, asteroids have a wide range of shape elongations, implying fragmentation-formation. In older families we see an increasing number of rough spheroids, in agreement with the predictions of an impact-driven evolution. Old families also contain a group of moderately elongated members, which we suggest correspond to higher-density, more impact-resistant cores of former fragmented asteroids that have undergone slow shape erosion. A few percent of asteroids have very elongated shapes, and can either be young fragments or tidally reshaped bodies. Our results confirm that the majority of asteroids are gravitationally bound ``rubble piles''.
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