Formation and Destruction of Small Binary Asteroids
Formation and Destruction of Small Binary Asteroids
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DOI：
10.1086/516572
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发表时间：
2007-03
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影响因子：
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通讯作者：
M. Ćuk
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作者：
M. Ćuk
我们对双星小行星的理解目前正在进行重大修订。直到最近，所有已知的小型联星（主直径小于等于1公里）都是近地小行星，这使得它们可能起源于与类地行星的近距离碰撞，而不是在主带小行星中发现的。第一次模拟潮汐破裂产生的双星的发生率大致匹配观测到的双星近地小行星的比例。热辐射效应，特别是Yarkovsky-O 'Keefe-Radzievskii-Paddack（英语：Yarkovsky-O' Keefe-Radzievskii-Paddack），并不需要用来解释双星小行星的生命周期，尽管有一些理论论据支持YORP的演化。最近发现了大量的小型MBA双星，并对行星相遇的影响进行了更加自洽的重新评估，这使行星相遇的首要地位受到怀疑，并表明需要新的理论解释。在这里，我表明，从主要的表面由于YORP的质量损失可以解释的形成更大规模的二元近地小行星。我还认为，小分离NEA双星的观察到的属性是一致的演变通过“二进制YORP”，而不是潮汐剥离在行星通道（当对演变超过10主半径，遇到变得重要）。这样的生命周期不仅意味着小型双星小行星非常年轻（<105年），而且大多数较小的小行星大规模质量重新分布的时间尺度也很短，导致其表面几乎完全没有陨石坑。
Our understanding of binary asteroids is currently undergoing major revisions. Until recently, all known small binaries (primary diameters ≃1 km) were near-Earth asteroids (NEAs), making it plausible that they originate in close encounters with terrestrial planets, and were not to be found among the main belt asteroids (MBAs). First simulations of tidal disruption have produced incidence of binaries that roughly matched the observed fraction of binary NEAs. Thermal-radiation effects, most notably YORP (Yarkovsky-O'Keefe-Radzievskii-Paddack), were not needed to explain the life cycle of binary asteroids, despite some theoretical arguments in favor of significant YORP evolution. Recent discovery of abundant small MBA binaries and a more self-consistent reassessment of effects of planetary encounters have put the primacy of planetary encounters in doubt and shown a need for new theoretical explanations. Here I show that the mass loss from the primary's surface due to YORP could explain the formation of kilometer-sized binary NEAs. I also suggest that the small-separation NEA binaries' observed properties are consistent with evolution through "binary YORP," rather than tidal stripping during planetary passages (when the pairs evolve beyond ~10 primary radii, encounters become important). Such a life cycle implies not only the extreme youth of small binary asteroids (<105 yr) but also short timescales for large-scale mass redistribution on most kilometer-sized asteroids, leading to a near-complete lack of craters on their surfaces.