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arXiv 2005.05000astro-ph.EP
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原水星和原金星在类地行星形成中的极端近距离相遇

Extreme close encounters between proto-Mercury and proto-Venus in terrestrial planet formation

Tong Fang, Hongping Deng

摘要:

现代的类地行星形成模型需要在微行星盘中的0.5-0.7金的固体耗尽来解释水星的小质量。地球和金星类似物出现后,约1亿年的碰撞增长,而水星形成的扩散尾巴的星子盘。我们对质量限制在0.7-1.0 au的小行星盘进行了250次N体模拟,以研究Deng(2020)最近提出的近距离接触的统计数据,作为对水星高铁质量分数的解释。我们总共形成了39个水星类似物,所有的原水星类似物都被原金星分散在内部。在原金星获得0.7金星质量后,原水星通常会经历6次与原金星的极端近距离接触(最接近小于6金星半径)。在如此近的距离,潮汐相互作用已经可以显著地影响轨道运动,使得N体处理本身无效。如果考虑到轨道角动量的潮汐耗散,预计会有更多更近的相遇。混合N体流体动力学模拟,治疗轨道和遇到动力学自洽,是可取的评估程度的潮汐地幔剥离的原水星。

英文摘要:

Modern models of terrestrial planet formation require solids depletion interior to 0.5-0.7 au in the planetesimal disk to explain the small mass of Mercury. Earth and Venus analogues emerge after ~100 Myr collisional growth while Mercury form in the diffusive tails of the planetesimal disk. We carried out 250 N-body simulations of planetesimal disks with mass confined to 0.7-1.0 au to study the statistics of close encounters which were recently proposed as an explanation for the high iron mass fraction in Mercury by Deng (2020). We formed 39 Mercury analogues in total and all proto-Mercury analogues were scattered inward by proto-Venus. Proto-Mercury typically experiences 6 extreme close encounters (closest approach smaller than 6 Venus radii) with Proto-Venus after Proto-Venus acquires 0.7 Venus Mass. At such close separation, the tidal interaction can already affect the orbital motion significantly such that the N-body treatment itself is invalid. More and closer encounters are expected should tidal dissipation of orbital angular momentum accounted. Hybrid N-body hydrodynamic simulations, treating orbital and encounter dynamics self-consistently, are desirable to evaluate the degree of tidal mantle stripping of proto-Mercury.

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