Effects of Type I Migration on Terrestrial Planet Formation
Effects of Type I Migration on Terrestrial Planet Formation
复制标题
I 型迁移对类地行星形成的影响
DOI：
10.1086/497687
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
H. Levison
中科院分区：
文献类型：
--
作者：
Douglas McNeil;M. Duncan;H. Levison
嵌入气盘中的行星胚胎遭受半长轴衰减-I型迁移-这是由于天体产生的内部和外部尾流产生的不对称扭矩。这对形成类地行星的标准寡头方法提出了挑战，因为在1 Au附近生长祖天体的时间尺度比它们衰变到太阳的时间要长。在本文中，我们调查的中期和后期阶段的寡头增长，使用半解析方法（基于Alummes和同事）和N体积分和不同的气体性质，如在不同模型的原行星盘的耗散时标。我们的结论是，即使在接近名义的迁移效率和1.1亿年的气体消散时间尺度下，如果盘质量比最小质量模型增加1.2 -4倍，那么陆地区域也有可能保持足够的质量来形成地球和金星。由此产生的结构在几个方面不同于先前模拟陆地吸积最后阶段所使用的初始条件，主要是（1）更大的胚间间距，（2）更大的胚胎质量，（3）当气体消失时，以微行星形式留下的物质高达10.4兆焦耳。我们所产生的系统在1000万年内相当稳定，因此需要一个外部来源来充分搅动胚胎，以产生类似于类地行星的最终系统。
Planetary embryos embedded in a gas disk suffer a decay in semimajor axis—type I migration—due to the asymmetric torques produced by the interior and exterior wakes raised by the body. This presents a challenge for standard oligarchic approaches to forming the terrestrial planets, as the timescale to grow the progenitor objects near 1 AU is longer than that for them to decay into the Sun. In this paper we investigate the middle and late stages of oligarchic growth using both semianalytic methods (based on Thommes and coworkers) and N-body integrations and vary gas properties such as dissipation timescale in different models of the protoplanetary disk. We conclude that even for near-nominal migration efficiencies and gas dissipation timescales of ∼1 Myr, it is possible to maintain sufficient mass in the terrestrial region to form Earth and Venus if the disk mass is enhanced by factors of ∼2–4 over the minimum-mass model. The resulting configurations differ in several ways from the initial conditions used in previous simulations of the final stages of terrestrial accretion, chiefly in (1) larger interembryo spacings, (2) larger embryo masses, and (3) up to ∼0.4 M⊕ of material left in the form of planetesimals when the gas vanishes. The systems we produce are reasonably stable for ∼100 Myr and therefore require an external source to stir up the embryos sufficiently to produce final systems resembling the terrestrial planets.