Formation of terrestrial planets from protoplanets. I. Statistics of basic dynamical properties
Formation of terrestrial planets from protoplanets. I. Statistics of basic dynamical properties
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DOI：
10.1086/501448
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发表时间：
2006-05-10
影响因子：
4.9
通讯作者：
Ida, S
中科院分区：
文献类型：
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作者：
Kokubo, E;Kominami, J;Ida, S
类地行星形成的最后阶段被称为巨撞击阶段，在此阶段原行星相互碰撞形成行星。由于这个过程是随机的，为了阐明它，有必要进行统计量化。我们利用N体模拟研究从原行星到类地行星的这一最终组合。作为初始条件，我们采用原行星的寡头生长模型。我们系统地改变初始原行星系统的表面密度、表面密度分布和轨道间距以及原行星的体密度，而初始系统的径向范围固定在0.5 - 1.5天文单位。对于每种初始条件，我们进行20次模拟，从结果中得出组合行星的统计特性。对于标准盘模型，通常在类地行星区域会形成两颗地球大小的行星。我们展示了行星的质量和轨道要素对初始原行星系统参数的依赖性，并给出了它们简单的经验拟合。随着初始原行星表面密度的增加，行星的数量缓慢减少，而单个行星的质量几乎呈线性增加。对于更陡的表面密度分布，大行星往往更靠近恒星形成。在我们所测试的参数范围内，只要总质量固定，行星系统的基本结构仅略微依赖于原行星的初始分布和体密度。
The final stage of terrestrial planet formation is known as the giant impact stage, where protoplanets collide with one another to form planets. As this process is stochastic, in order to clarify it, it is necessary to quantify it statistically. We investigate this final assemblage of terrestrial planets from protoplanets using N-body simulations. As initial conditions, we adopt the oligarchic growth model of protoplanets. We systematically change the surface density, surface density profile, and orbital separation of the initial protoplanet system, and the bulk density of protoplanets, while the initial system radial range is fixed at 0.5-1.5 AU. For each initial condition, we perform 20 runs, and from their results we derive the statistical properties of the assembled planets. For the standard disk model, typically two Earth-sized planets form in the terrestrial planet region. We show the dependences of the masses and orbital elements of planets on the initial protoplanet system parameters and give their simple empirical fits. The number of planets slowly decreases as the surface density of the initial protoplanets increases, while the masses of individual planets increase almost linearly. For a steeper surface density profile, large planets tend to form closer to the star. For the parameter ranges that we test, the basic structure of planetary systems depends only slightly on the initial distribution of protoplanets and the bulk density as long as the total mass is fixed.