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arXiv 1209.6033astro-ph.EP
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行星对小天体的散射:一种可能的外黄道尘的起源?

Scattering of small bodies by planets: a potential origin for exozodiacal dust ?

Amy Bonsor, Jean-Charles Augereau, Philippe Thebault

摘要:

在越来越多的主序星周围观测到高水平的黄外尘埃。这种尘埃的起源尚不清楚,因为它在碰撞和辐射力下的寿命很短。即使是一个碰撞级联与公里大小的母体,建议解释外部碎片盘,不能生存足够长的时间。在这项工作中,我们调查所观察到的exozodiacal灰尘是否可以起源于外星子带。我们调查的散射过程中稳定的行星系,以确定是否有足够的材料可以分散向内,以保持其目前观察到的水平的exozodiacal尘埃。我们使用N体模拟调查这种散射的效率和它对行星系结构的依赖。这些模拟的结果可以用来评估假设的行星链在观测系统中产生exozodi的能力。我们发现,对于年龄更大(> 1亿年)的恒星,如果有外黄道尘埃,则需要一个大质量、大半径(> 20天文单位)的外带和一系列紧密堆积的低质量行星,才能将尘埃保持在目前观测到的水平。这就产生了一个问题,如果有的话,有多少真实的系统拥有这样一个人为的结构,因此能够以足够高的速度散射,以保持长时间尺度的exozodi尘埃。

英文摘要:

High levels of exozodiacal dust are observed around a growing number of main sequence stars. The origin of such dust is not clear, given that it has a short lifetime against both collisions and radiative forces. Even a collisional cascade with km-sized parent bodies, as suggested to explain outer debris discs, cannot survive sufficiently long. In this work we investigate whether the observed exozodiacal dust could originate from an outer planetesimal belt. We investigate the scattering processes in stable planetary systems in order to determine whether sufficient material could be scattered inwards in order to retain the exozodiacal dust at its currently observed levels. We use N-body simulations to investigate the efficiency of this scattering and its dependence on the architecture of the planetary system. The results of these simulations can be used to assess the ability of hypothetical chains of planets to produce exozodi in observed systems. We find that for older (>100Myr) stars with exozodiacal dust, a massive, large radii (>20AU) outer belt and a chain of tightly packed, low-mass planets would be required in order to retain the dust at its currently observed levels. This brings into question how many, if any, real systems possess such a contrived architecture and are therefore capable of scattering at sufficiently high rates to retain exozodi dust on long timescales.

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