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，为了研究行星的生长速率和自转的起源，有必要获得两个碰撞物体之间的质量和角动量重新分布的信息。我们已经开始了一系列关于这一主题的系统研究，这是我们的第一份报告。我们集中在一个原行星，其中有一个地球质量，和另一个原行星与0.06地球质量之间的影响。用SPH方法对两个物体的运动进行了数值模拟。我们改变两个天体之间的最小距离作为参数来指定它们的轨道角动量。对于每个参数值，我们重复数值模拟，并获得最终的机构。这些不同的最终状态检查的标准，以区分一些集群形成的许多SPH粒子。我们确定中央原行星和每个集群之间的相对运动的瞬时轨道要素。根据这些信息，我们预测每个集群的命运，例如合并到目标体内或被困。然后确定初始条件，得到最终的特征态.这5种状态是撞击物被吸收到目标上的合并状态、撞击物与目标反复碰撞的多次撞击状态、撞击物被潮汐地破坏并且撞击物的大部分从目标逃逸的破坏逃逸状态、撞击物被目标捕获的捕获状态、以及撞击物照原样通过的通过状态。

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.