Dynamical Evolution Induced by Planet Nine
Dynamical Evolution Induced by Planet Nine
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DOI：
10.3847/1538-3881/aa937c
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发表时间：
2017-10
期刊：
影响因子：
--
通讯作者：
K. Batygin;A. Morbidelli
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文献类型：
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作者：
K. Batygin;A. Morbidelli
对半长轴大于的跨海王星天体的观测普查显示出意想不到的轨道结构，这最容易被归因于一颗尚未被探测到的大质量行星引起的引力扰动。尽管这颗行星有能力(I)重现观测到的物理空间中遥远轨道的集群，(Ii)促进其近日点动态脱离海王星，以及(Iii)通过数值实验激发长周期半人马种群向极端倾斜，但对导致这些效应的动力学机制的连贯理论描述仍然难以捉摸。在这项工作中，我们从半解析的角度刻画了所起作用的动力学过程。我们首先考虑由行星九引起的轨道演化的纯长期模型，并表明它与随之而来的遥远物体的稳定性是不一致的。相反，长周期柯伊伯带天体(KBO)的集群种群的长期生存是由九号行星驱动的平均运动共振网络实现的。然后，通过采用紧凑形式的微扰理论，我们证明了是嵌入在这些共振中的长期动力学调节了遥远的KBO的轨道约束和近日点脱离。最后，我们论证了轨道倾角的大幅度振荡的开始是通过捕获低倾角物体进入高阶长期共振来完成的，并确定了驱动演化的特定谐波。鉴于对支配动力学的定性理解的发展，我们在行星九假说的更广泛的理论框架内对当前的观测数据集提供了最新的解释。
The observational census of trans-Neptunian objects with semimajor axes greater than exhibits unexpected orbital structure that is most readily attributed to gravitational perturbations induced by a yet-undetected, massive planet. Although the capacity of this planet to (i) reproduce the observed clustering of distant orbits in physical space, (ii) facilitate the dynamical detachment of their perihelia from Neptune, and (iii) excite a population of long-period centaurs to extreme inclinations is well-established through numerical experiments, a coherent theoretical description of the dynamical mechanisms responsible for these effects remains elusive. In this work, we characterize the dynamical processes at play from semi-analytic grounds. We begin by considering a purely secular model of orbital evolution induced by Planet Nine and show that it is at odds with the ensuing stability of distant objects. Instead, the long-term survival of the clustered population of long-period Kuiper Belt objects (KBOs) is enabled by a web of mean-motion resonances driven by Planet Nine. Then, by taking a compact-form approach to perturbation theory, we show that it is the secular dynamics embedded within these resonances that regulate the orbital confinement and perihelion detachment of distant KBOs. Finally, we demonstrate that the onset of large-amplitude oscillations of the orbital inclinations is accomplished through the capture of low-inclination objects into a high-order secular resonance, and we identify the specific harmonic that drives the evolution. In light of the developed qualitative understanding of the governing dynamics, we offer an updated interpretation of the current observational data set within the broader theoretical framework of the Planet Nine hypothesis.