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arXiv 1907.09809astro-ph.EP
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天王星和海王星历史上的分叉:巨大撞击的作用

Bifurcation in the history of Uranus and Neptune: the role of giant impacts

Christian Reinhardt, Alice Chau, Joachim Stadel, Ravit Helled

摘要:

尽管有许多相似之处,但天王星和海王星之间有着显著的观测差异:天王星是倾斜的,并且有一组规则的卫星,这表明它们是从圆盘中吸积而来的,而海王星的卫星是不规则的,是被捕获的物体。此外,海王星似乎有一个内部热源,而天王星与太阳绝缘处于平衡状态。最后,基于重力数据的结构模型表明,天王星比海王星更集中。我们进行了一系列高分辨率的SPH模拟,以研究这些差异是否可以用巨大的撞击来解释。对于天王星,我们发现倾斜的撞击可以使其旋转轴倾斜,并喷射出足够的物质来形成一个形成常规卫星的圆盘。有些圆盘是巨大的,并且足够延伸,由足够的岩石材料组成,可以解释天王星规则卫星的形成。对于海王星,我们研究了正面碰撞是否会混合内部,并导致绝热温度分布,这可能解释其较大的通量和较高的转动惯量值。我们发现,大质量和密集的抛射体可以穿透到中心,并在内部深处沉积质量和能量,导致海王星的内部集中度较低。我们的结论是,冰巨人之间的二分法可以用它们形成后的猛烈撞击来解释。

英文摘要:

Despite many similarities, there are significant observed differences between Uranus and Neptune: while Uranus is tilted and has a regular set of satellites, suggesting their accretion from a disk, Neptune's moons are irregular and are captured objects. In addition, Neptune seems to have an internal heat source, while Uranus is in equilibrium with solar insulation. Finally, structure models based on gravity data suggest that Uranus is more centrally condensed than Neptune. We perform a large suite of high resolution SPH simulations to investigate whether these differences can be explained by giant impacts. For Uranus, we find that an oblique impact can tilt its spin axis and eject enough material to create a disk where the regular satellites are formed. Some of the disks are massive and extended enough, and consist of enough rocky material to explain the formation of Uranus' regular satellites. For Neptune, we investigate whether a head-on collision could mix the interior, and lead to an adiabatic temperature profile, which may explain its larger flux and higher moment of inertia value. We find that massive and dense projectiles can penetrate towards the centre and deposit mass and energy in the deep interior, leading to a less centrally concentrated interior for Neptune. We conclude that the dichotomy between the ice giants can be explained by violent impacts after their formation.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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