Embedded star clusters and the formation of the Oort cloud - II. The effect of the primordial solar nebula
Embedded star clusters and the formation of the Oort cloud - II. The effect of the primordial solar nebula
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DOI：
10.1016/j.icarus.2007.05.003
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发表时间：
2007-11-15
期刊：
影响因子：
3.2
通讯作者：
Levison, H. F.
中科院分区：
文献类型：
--
作者：
Brasser, R.;Duncan, M. J.;Levison, H. F.
本文研究了太阳处于嵌入星团并被原始星云包围时奥尔特云的形成。这项工作是Brasser等人的延续。Brasser， R., Duncan， M., Levison， H., 2006。伊卡洛斯184,59-82]，在其中提出的模型的基础上，并加入了原始太阳星云的空气动力学阻力和引力势。介绍了受太阳、木星、土星、星团和原始太阳星云引力影响的彗星的数值模拟结果；其中一些模拟还包括天王星和海王星的引力影响。原始太阳星云是由最小质量Hayashi模型近似的[Hayashi， C., Nakozawa， K., Nakagawa， Y., 1985]。见：Black， d.c., Matthews， M.S.（编辑）。原恒星和行星2。[亚利桑那大学出版社，图森，亚利桑那州]其内外半径在与太阳的不同距离上被截断。我们的大多数模拟使用了一颗直径1.7公里的彗星。在我们所有的模拟中，原始太阳星云的密度呈指数衰减，电子折叠时间为2myr。事实证明，当原始太阳星云延伸到土星或海王星之外时，在这一阶段几乎没有物质会最终进入奥尔特云（CC）。相反，如果圆盘的内缘在木星轨道内，大部分物质将在木星内部的圆形轨道上运行。如果圆盘的内缘在木星轨道之外，当天王星和海王星不存在时，大多数彗星最终会在与土星的外部平均运动共振的轨道上运行。在那些圆盘外缘靠近土星或海王星的情况下，最终形成OC的物质比例比Brasser等人发现的要少得多[Brasser， R., Duncan， M., Levison， H., 2006]。Icarus 184,59 -82]，得到相同的星团密度。这意味着对于大约2公里大小的彗星，原始太阳星云的存在阻碍了OC的形成。我们的一些模拟的副产品是天王星-海王星分散盘中相当一部分彗星的最终结果。计划在不久的将来对这些材料进行后续研究。为了确定彗星的大小对OC形成效率的影响，我们还进行了一组初始条件相同但彗星半径不同的运行，从中可以确定开始产生显著奥尔特云的彗星大小的阈值大约是20公里。这意味着，在研究的模型中，原始太阳星云的存在起到了一种大小分类机制的作用，大天体不受气体阻力的影响，最终进入OC，而小天体则被困在行星区域。(C) 2007爱思唯尔公司版权所有。
This paper deals with Oort cloud formation while the Sun was in an embedded cluster and surrounded by its primordial nebula. This work is a continuation of Brasser et a]. [Brasser, R., Duncan, M., Levison, H., 2006. Icarus 184, 59-82], building on the model presented therein, and adding the aerodynamic drag and gravitational potential of the primordial solar nebula. Results are presented of numerical simulations of comets subject to the gravitational influence of the Sun, Jupiter, Saturn, star cluster and primordial solar nebula; some of the simulations included the gravitational influence of Uranus and Neptune as well. The primordial solar nebula was approximated by the minimum-mass Hayashi model [Hayashi, C., Nakozawa, K., Nakagawa, Y., 1985. In: Black, D.C., Matthews, M.S. (Eds.). Protostars and Planets II. Univ. of Arizona Press, Tucson, AZ] whose inner and outer radii have been truncated at various distances from the Sun. A comet size of 1.7 km was used for most of our simulations. In all of our simulations, the density of the primordial solar nebula decayed exponentially with an e-folding time of 2 Myr. It turns out that when the primordial solar nebula extends much beyond Saturn or Neptune, virtually no material will end up in the Oort cloud (CC) during this phase. Instead, the majority of the material will be on circular orbits inside of Jupiter if the inner edge of the disk is well inside Jupiter's orbit. If the disk's inner edge is beyond Jupiter's orbit, most comets end up on orbits in exterior mean-motion resonances with Saturn when Uranus and Neptune are not present. In those cases where the outer edge of the disk is close to Saturn or Neptune, the fraction of material that ends up in the subsequently formed OC is much less than that found in Brasser et al. [Brasser, R., Duncan, M., Levison, H., 2006. Icarus 184, 59-82] for the same cluster densities. This implies that for comets of roughly 2 km in size, the presence of the primordial solar nebula hinders OC formation. A byproduct of some of our simulations are endresults with a substantial fraction of the comets in the Uranus-Neptune scattered disk. A subsequent followup of this material is planned for the near future. In order to determine the effect of the size of the comets on OC formation efficiency, a set of runs with the same initial conditions but different cometary radii have been performed as well, from which it is determined that the threshold comet size to begin producing significant Oort clouds is roughly 20 km. This implies that the presence of the primordial solar nebula acts as a size-sorting mechanism, with large bodies unaffected by the gas drag and ending up in the OC while small bodies remain trapped in the planetary region, in the models studied. (C) 2007 Elsevier Inc. All rights reserved.