100-metre-diameter moonlets in Saturn's A ring from observations of 'propeller' structures
100-metre-diameter moonlets in Saturn's A ring from observations of 'propeller' structures
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土星 A 环中直径 100 米的小卫星来自“螺旋桨”结构的观测
DOI：
10.1038/nature04581
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发表时间：
2006
期刊：
影响因子：
64.8
通讯作者：
C. Murray
中科院分区：
文献类型：
--
作者：
M. Tiscareno;J. Burns;M. Hedman;C. Porco;J. W. Weiss;L. Dones;D. Richardson;C. Murray
土星的主环主要由水冰粒子组成，其半径在1厘米到10米之间。根据宇宙飞船和恒星掩星的解释，在这个大小范围以上，粒子的数量急剧下降。除了间隙卫星“潘”和“Daphnis”（暂定名为S/2005 S1），这两颗卫星的大小都有几公里，在环中没有单独的天体被直接观察到，而大于10米的环粒子的数量基本上是未知的。在这里，我们报告四个纵向双条纹的观察，否则平淡的部分中a环。我们推断，这些“螺旋桨”形状的扰动是由直径约40至120米的嵌入小卫星的影响引起的。对这一现象的直接观察证实了原行星盘的模型，其中假设了类似的过程。根据我们发现的大小分布，大量的小卫星可以帮助解释卡西尼分裂和C环更脆弱区域的间隙。如此大的嵌入小卫星的存在与一个起源于较大天体分裂的环的存在是最自然的相容的，但是，如果在最初的吸积阶段结束后，大颗粒的后续生长发生在环绕行星的圆盘上，这也是合理的。
Saturn's main rings are composed predominantly of water-ice particles ranging between about 1 centimetre and 10 metres in radius. Above this size range, the number of particles drops sharply, according to the interpretation of spacecraft and stellar occultations. Other than the gap moons Pan and Daphnis (the provisional name of S/2005 S1), which have sizes of several kilometres, no individual bodies in the rings have been directly observed, and the population of ring particles larger than ten metres has been essentially unknown. Here we report the observation of four longitudinal double-streaks in an otherwise bland part of the mid-A ring. We infer that these ‘propeller’-shaped perturbations arise from the effects of embedded moonlets approximately 40 to 120 m in diameter. Direct observation of this phenomenon validates models of proto-planetary disks in which similar processes are posited. A population of moonlets, as implied by the size distribution that we find, could help explain gaps in the more tenuous regions of the Cassini division and the C ring. The existence of such large embedded moonlets is most naturally compatible with a ring originating in the break-up of a larger body, but accretion from a circumplanetary disk is also plausible if subsequent growth onto large particles occurs after the primary accretion phase has concluded.
土星环中小卫星引起的结构：对卡西尼号任务的影响
影响因子：
5.2
作者：
Sremčevič
通讯作者：
Sremčevič