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有读书笔记The recent formation of Saturn's moonlets from viscous spreading of the main rings

Dr.LinZhen 添加于 2010-6-11 11:18 | 2549 次阅读 | 0 个评论
  •  作 者

    Charnoz S, Salmon J, Crida A
  •  摘 要

    The regular satellites of the giant planets are believed to have finished their accretion concurrent with the planets, about 4.5 Gyr ago1, 2, 3, 4. A population of Saturn’s small moons orbiting just outside the main rings are dynamically young5, 6 (less than 107 yr old), which is inconsistent with the formation timescale for the regular satellites. They are also underdense7 (~600 kg m−3) and show spectral characteristics similar to those of the main rings8, 9. It has been suggested that they accreted at the rings’ edge7, 10, 11, but hitherto it has been impossible to model the formation process fully owing to a lack of computational power. Here we report a hybrid simulation in which the viscous spreading of Saturn’s rings beyond the Roche limit (the distance beyond which the rings are gravitationally unstable) gives rise to the small moons. The moonlets’ mass distribution and orbital architecture are reproduced. The current confinement of the main rings and the existence of the dusty F ring are shown to be direct consequences of the coupling of viscous evolution and satellite formation. Saturn’s rings, like a mini protoplanetary disk, may be the last place where accretion was recently active in the Solar System, some 106–107 yr ago.
  •  详细资料

    • 文献种类:期刊
    • 期刊名称: Nature
    • 期刊缩写: Nature
    • 期卷页: 2010  465 7299 752-754
    • ISBN: 0028-0836
  • 相关链接 DOI URL 

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    土星小卫星的形成机制

    土星的一组较小的卫星与巨型行星的通常卫星形成鲜明对比。像土星的“土卫二”和木星的“木卫二”那样的卫星在它们主行星的赤道平面上运行,被认为是在与其主行星大约相同的时间(距今45亿年前)就已经完成了吸积过程。土星的冰质小卫星要年轻得多,是在不到1000万年前形成,而且由于它们的光谱与主环(卫星)的光谱相似,所以曾有人提出,它们是由在主环边缘发生的吸积形成的。对土星系统所做的一次混合数值模拟支持这一观点,说明这些卫星是通过土星主环向“洛希极限”(超过这个距离时,土星的环在引力上不稳定,这个位置距土星约140,000公里)的粘性扩散形成的。在这些卫星形成之后,环的边缘向里迁移。

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