Capture of the Sun's Oort Cloud from Stars in Its Birth Cluster
Capture of the Sun's Oort Cloud from Stars in Its Birth Cluster
复制标题
从太阳诞生星团中的恒星捕获太阳的奥尔特云
作者：
H. Levison;M. Duncan;R. Brasser;D. Kaufmann
长周期彗星起源于奥尔特云，奥尔特云是环绕太阳系的一个巨大的冰体储存库。这些天体被认为是太阳系形成时的残留物。但它们都是在太阳的原行星盘中形成的，还是在太阳可能形成的星团中其他恒星的原行星盘中产生的？Levison等人（第187页，6月10日在线发表）使用详细的数值模拟来研究有多少比例的彗星可能从一个恒星系统的外围转移到另一个恒星系统。模拟表明，通过这种机制可以捕获相当数量的彗星，这可能解释了为什么奥尔特云中的天体数量比模型预测的要多。一些奥尔特云彗星可能起源于其他恒星的原行星盘，而不是太阳。奥尔特云彗星目前被认为是在太阳的原行星盘中形成的，并被巨型行星喷射到大的日心轨道上。然而，这一过程的详细模型并不能再现所有可用的观测约束。特别是，奥尔特云的人口似乎比模型预测的要多得多。在这里，我们给出了数值模拟，表明太阳在它的诞生星团中捕获了来自其他恒星的彗星。我们的结果表明，奥尔特云彗星的很大一部分，可能超过90%，来自其他恒星的原行星盘。
Out of the Oort Cloud Long-period comets originate from the Oort cloud, a vast reservoir of icy bodies that surrounds the solar system. These bodies are thought to be remnants from the formation of the solar system. But did they all form in the Sun's protoplanetary disk, or could they have been generated in the protoplanetary disks of other stars in the cluster where the Sun probably formed? Levison et al. (p. 187, published online 10 June) used detailed numerical simulations to investigate what fraction of comets might transfer from the outer reaches of one stellar system to another. The simulations suggest that a substantial number of comets can be captured through this mechanism, which may explain why the number of bodies in the Oort cloud is larger than models predict. Some Oort cloud comets may have originated in the protoplanetary disk of stars other than the Sun. Oort cloud comets are currently believed to have formed in the Sun's protoplanetary disk and to have been ejected to large heliocentric orbits by the giant planets. Detailed models of this process fail to reproduce all of the available observational constraints, however. In particular, the Oort cloud appears to be substantially more populous than the models predict. Here we present numerical simulations that show that the Sun captured comets from other stars while it was in its birth cluster. Our results imply that a substantial fraction of the Oort cloud comets, perhaps exceeding 90%, are from the protoplanetary disks of other stars.