EVIDENCE FOR SLOW MIGRATION OF NEPTUNE FROM THE INCLINATION DISTRIBUTION OF KUIPER BELT OBJECTS
EVIDENCE FOR SLOW MIGRATION OF NEPTUNE FROM THE INCLINATION DISTRIBUTION OF KUIPER BELT OBJECTS
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DOI：
10.1088/0004-6256/150/3/73
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发表时间：
2015-04
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通讯作者：
D. Nesvorný
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作者：
D. Nesvorný
如果海王星在几个天文单位上迁移，或者海王星在行星不稳定期间分散到偏心轨道上，那么柯伊伯带的许多动力结构都可以解释。现有形成模型的一个突出问题是，它们预测的轨道倾角分布比观测推断的窄。在这里，我们对柯伊伯带的形成进行了数值模拟，从海王星在20天文单位的初始状态和一个从N， 0 ？>到30au。海王星的轨道在电子折叠时间尺度1≤τ≤100 Myr上迁移到盘上。在模拟中，一小部分（~ 10−3）的盘状星子被植入柯伊伯带。通过分析不同情况下植入体的轨道分布，我们发现倾角约束意味着τ≈10 ？> Myr和a N， 0≤25 ？>非盟。具有τ Myr的模型不满足倾角约束，因为各种动力过程没有足够的时间来提高倾角。海王星的缓慢迁移与柯伊伯带的其他限制是一致的，并且与最近发展的行星不稳定/迁移模型是一致的。在这些模型中，海王星的离心率和倾角从来都不是很大（e N, i N），这是为了避免在bbb40 AU区域（可能是冷经典星系形成的地方）中轨道受到过度激发所必需的。
Much of the dynamical structure of the Kuiper Belt can be explained if Neptune migrated over several AU, and/or if Neptune was scattered to an eccentric orbit during planetary instability. An outstanding problem with the existing formation models is that the distribution of orbital inclinations they predicted is narrower than the one inferred from observations. Here we perform numerical simulations of Kuiper Belt formation starting from an initial state with Neptune at 20 AU and a dynamically cold outer disk extending from beyond a N , 0 ?> to 30 AU. Neptune’s orbit is migrated into the disk on an e-folding timescale 1 ≤ τ ≤ 100 Myr. A small fraction (∼10−3) of the disk planetesimals become implanted into the Kuiper belt in the simulations. By analyzing the orbital distribution of the implanted bodies in different cases we find that the inclination constraint implies that τ ≳ 10 ?> Myr and a N , 0 ≲ 25 ?> AU. The models with τ Myr do not satisfy the inclination constraint, because there is not enough time for various dynamical processes to raise inclinations. The slow migration of Neptune is consistent with other Kuiper Belt constraints, and with recently developed models of planetary instability/migration. Neptune’s eccentricity and inclination are never large in these models ( e N , i N ), as required to avoid excessive orbital excitation in the >40 AU region, where the Cold Classicals presumably formed.