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arXiv 1102.1430astro-ph.EP
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利用柯伊伯带双星约束海王星的迁移历史

Using Kuiper Belt Binaries to Constrain Neptune's Migration History

Ruth A. Murray-Clay, Hilke E. Schlichting

摘要:

大约10-20%的柯伊伯带天体(KBO)与海王星有平均运动共振。这种动力学结构可能是由于海王星在行星形成的后期向外迁移时共振捕获的结果。海王星的微行星驱动迁移的细节,包括其径向范围和行星的同步偏心率演化,是相当大的辩论的主题。有两种性质不同的共振捕获提议被提出--海王星轨道平滑向外演化驱动的迁移诱导捕获和行星当前半长轴附近偏心率阻尼驱动的混沌捕获。我们证明,分布的可比质量,宽分离双星占据共振轨道可以区分这两种情况。如果发生迁移诱导的捕获,这部分记录的信息的形成位置的不同人口的KBO。相反,混沌俘获使处于共振状态的物体的轨道随机化。特别地,迁移诱导的捕获产生以下特征。2:1共振应包含动态冷分量,倾角小于5-10度,具有与冷经典KBO中的二元分数相当的二元分数。如果3:2共振也有冷的成分,它的双星分数应该比冷的经典带低20-30%。在冷的2:1(如果存在3:2)KBO中,偏心率e < 0.2的天体应该比e > 0.2的天体的双星分数大20%。共振KBO的二进制馏分中的冷组分的分离是目前实用的。这里描述的其他迁移产生的趋势可能与LSST发现的物体不同。(摘要节略)

英文摘要:

Approximately 10-20% of all Kuiper belt objects (KBOs) occupy mean-motion resonances with Neptune. This dynamical configuration likely resulted from resonance capture as Neptune migrated outward during the late stages of planet formation. The details of Neptune's planetesimal-driven migration, including its radial extent and the concurrent eccentricity evolution of the planet, are the subject of considerable debate. Two qualitatively different proposals for resonance capture have been proposed--migration-induced capture driven by smooth outward evolution of Neptune's orbit and chaotic capture driven by damping of the planet's eccentricity near its current semi-major axis. We demonstrate that the distribution of comparable-mass, wide-separation binaries occupying resonant orbits can differentiate between these two scenarios. If migration-induced capture occurred, this fraction records information about the formation locations of different populations of KBOs. Chaotic capture, in contrast, randomizes the orbits of bodies as they are placed in resonance. In particular, migration-induced capture produces the following signatures. The 2:1 resonance should contain a dynamically cold component, with inclinations less than 5-10 degrees, having a binary fraction comparable to that among cold classical KBOs. If the 3:2 resonance also hosts a cold component, its binary fraction should be 20-30% lower than in the cold classical belt. Among cold 2:1 (and if present 3:2) KBOs, objects with eccentricities e < 0.2 should have a binary fraction ~20% larger than those with e > 0.2. Searches for cold components in the binary fractions of resonant KBOs are currently practical. The additional migration-generated trends described here may be distinguished with objects discovered by LSST. (Abstract abridged.)

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