Giant impacts between proto planets and late stage planetary accumulation

原行星之间的碰撞是行星形成过程后期的常见事件。原行星通过这些碰撞事件成长为现在的行星。因此，有必要获得有关碰撞的两个物体之间的质量和角动量重新分布的信息，以便研究行星的增长率及其自转的起源。我们已经针对这个主题开始了一系列系统的研究，这是我们的第一份报告。我们专注于一颗具有 1 个地球质量的原行星与另一颗具有 0.06 个地球质量的原行星之间的撞击。通过 SPH 模拟方法对两个物体的运动进行数值模拟。我们改变两个物体之间的最小距离作为参数来指定它们的轨道角动量。对于参数的每个值，我们重复数值模拟并获得物体的最终状态。这些不同的最终状态通过为区分由许多 SPH 粒子形成的一些簇而制定的标准来检查。我们确定中心原行星和每个星团之间相对运动的瞬时轨道元素。根据这些信息，我们预测每个簇的命运，例如合并到目标体中或被困住。然后我们确定最终特征状态的初始条件结果。这5种状态分别是冲击体被目标吸收的合并状态、冲击体与目标反复碰撞的多重冲击状态、冲击体被潮汐破坏且冲击体的大部分脱离目标的破坏逃逸状态、冲击体被目标捕获的捕获状态以及冲击体直接穿过的通过状态。

Collisions between protoplanets are common events in the later stage of planetary formation process. Protoplanets grew into present planets through these collisional events. So it is necessary to obtain information about redistribution of mass and angular momentum between colliding two bodies in order to study the growth rates of planets and the origin of their spin. We have started a series of systematic studies on this theme and this is our first report. We concentrate on the impact between one proto planet, which has one Earth mass, and another protoplanet with 0.06 Earth mass. The motion of two bodies are pursued numerically by the SPH simulation method. We change the minimum distance between the two bodies as parameter to specify the orbital angular momentum of them. For each value of the parameter, we repeated the numerical simulations and obtain final states of bodies. Such various final states are examined by criteria developed to distinguish some clusters formed by many SPH particles. We determine instantaneous orbital elements for relative motion between central protoplanet and each cluster. From this information we forecast the destiny of each cluster, for examples to be merged into the target body or trapped. Then we determine initial conditions result to final characteristic states. The 5 states are merging state in which the impactor absorbed to the target, multiple impact state in which the impactor collide with the target again and again, disruption escaping state in which the impactor is tidally disrupted and a large part of the impactor escapes from the target, trapping state in which the impactor is trapped by the target, and passing state in which the impactor passes through as it is.