arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2005.12887astro-ph.EP
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天王星系统的动力学历史

Dynamical History of the Uranian System

Matija Ćuk, Maryame El Moutamid, Matthew S. Tiscareno

摘要:

我们数值模拟天王星的五个大卫星(米兰达,阿里尔,Umbriel,泰坦尼亚和Oberon)过去的潮汐演化。我们发现,最近的主要平均运动共振(MMR)之间的任何两个卫星,Ariel-Umbriel 5:3 MMR,对整个系统有很大的影响。我们的研究结果表明,这种共振是负责目前的4.3 $^{\circ}$倾角的米兰达(而不是以前提出的3:1米兰达-Umbriel MMR),所有五个卫星都有自己的倾角在这种共振激发。米兰达在Ariel-Umbriel 5:3 MMR期间经历了显着的潮汐加热,这是由于它的偏心率被Ariel的长期扰动所激发。这种潮汐加热从米兰达轨道的收缩中吸取能量,而不是从阿里尔的向外演化中吸取能量,并能产生超过100 mW m $^{-2}$的热流,足以在米兰达上产生年轻的日冕。我们发现MMR之后是一系列的长期共振,重新洗牌的卫星的偏心率和倾斜度。我们还发现Oberon自旋轴的进动与Umbriel轨道面的进动接近共振,并且这种自旋-轨道共振很可能是在Ariel-Umbriel 5:3 MMR期间激发的。离开MMR后,随后的Ariel-Umbriel长期共振和Oberon-Umbriel自旋轨道共振可能能够解释Ariel和Umbriel当前的低倾角。米兰达表面特征的年龄初步建议天王星潮汐$Q=15,000-20,000$,这可以在未来的工作中进一步完善。

英文摘要:

We numerically simulate the past tidal evolution of the five large moons of Uranus (Miranda, Ariel, Umbriel, Titania, and Oberon). We find that the most recent major mean-motion resonance (MMR) between any two moons, the Ariel-Umbriel 5:3 MMR, had a large effect on the whole system. Our results suggest that this resonance is responsible for the current 4.3$^{\circ}$ inclination of Miranda (instead of previously proposed 3:1 Miranda-Umbriel MMR), and that all five moons had their inclinations excited during this resonance. Miranda experienced significant tidal heating during the Ariel-Umbriel 5:3 MMR due to its eccentricity being excited by Ariel's secular perturbations. This tidal heating draws energy from shrinking of Miranda's orbit, rather than Ariel's outward evolution, and can generate heat flows in excess of 100 mW m$^{-2}$, sufficient to produce young coronae on Miranda. We find that this MMR was followed by a sequence of secular resonances, which reshuffled the moons' eccentricities and inclinations. We also find that the precession of Oberon's spin axis is close to a resonance with the precession of Umbriel's orbital plane, and that this spin-orbit resonance was likely excited during the Ariel-Umbriel 5:3 MMR. After the exit from the MMR, subsequent Ariel-Umbriel secular resonance and Oberon-Umbriel spin-orbit resonance may be able to explain the current low inclinations of Ariel and Umbriel. The age of Miranda's surface features tentatively suggests Uranian tidal $Q=15,000-20,000$, which can be further refined in future work.

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