A New Mechanism Relevant to the Formation of Planetesimals in the Solar Nebula
A New Mechanism Relevant to the Formation of Planetesimals in the Solar Nebula
复制标题
与太阳星云中星子形成相关的新机制
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
J. Colwell
中科院分区：
文献类型：
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作者：
G. Wurm;J. Blum;J. Colwell
摘要目前的模型，形成公里大小的行星积木，或星子，碰撞吸积需要不切实际的低碰撞速度或特设的假设，为了增长发生。原行星状星云中的碰撞速度随着粒子大小的增加而增加，导致碰撞物体的反弹和破碎，而不是增长。我们描述了一种新的和有效的机制，在星子吸积，导致净增长，尽管碎片，至少对于小的星子。我们的实验结果显示，星云气流会将原行星尘埃颗粒还原为成长中的微行星，导致撞击速度至少达到10-15 ms−1时的吸积。这个新的阈值速度比宏观冰球之间的阈值速度高出三个数量级，比微米级尘埃颗粒的粘附速度高出十倍。
Abstract Current models of the formation of km-sized planetary building blocks, or planetesimals, by collisional accretion require unrealistically low collision velocities or ad hoc assumptions about sticking in order for growth to occur. Collision velocities in the protoplanetary nebula increase with increasing particle size, leading to bouncing and fragmentation of colliding bodies rather than growth. We describe a new and efficient mechanism in planetesimal accretion which leads to net growth in spite of fragmentation, at least for small planetesimals. Our experimental results show that nebular gas flow returns protoplanetary dust grains to a growing planetesimal, resulting in accretion for impact speeds up to at least 10–15 ms−1. This new threshold velocity is three orders of magnitude higher than the threshold velocity for accretion between macroscopic ice spheres and ten times higher than the sticking velocity for micron-sized dust particles.