The effects of disk building on the distributions of refractory materials in the solar nebula
The effects of disk building on the distributions of refractory materials in the solar nebula
复制标题
圆盘构建对太阳星云中耐火材料分布的影响
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
F. Ciesla
中科院分区：
文献类型：
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作者：
Le Yang;F. Ciesla
摘要：富含钙铝包裹体（CAI）和结晶硅酸盐等耐火材料广泛存在于球粒陨石和彗星中，被视为太阳星云中大规模混合的证据。大多数太阳星云混合模型都是从结构良好的原行星盘开始的。在这里，我们通过模拟太阳星云从其母体分子云吸积物质期间和之后的形成和演化来放松这一假设。我们考虑盘的构建如何影响盘的长期演化以及对盘内谷物运输和混合的影响。我们的模型表明，在坠落完成之前形成的物质可以保存在原始物体中，尤其是那些在外盘中积聚的物质。这可能解释了彗星中初始 26Al/27Al 比率较低的难熔物体的发现。我们的模型还表明，陨石中耐火材料的最高比例是在陨石停止时形成的。因此，我们认为球粒陨石中富含钙铝的包裹体将主要由年轻恒星从 I 类到 II 类阶段过渡期间形成的群体所主导。这有助于我们理解太阳系年表中t = 0的含义。此外，我们的模型为耐火材料中观察到的同位素变化的存在提供了可能的解释——异常材料是在母体分子云塌陷完成之前形成的。
Abstract– Refractory materials, such as calcium‐aluminum‐rich inclusions (CAIs) and crystalline silicates, are widely found in chondritic meteorites as well as comets, taken as evidence for large‐scale mixing in the solar nebula. Most models for mixing in the solar nebula begin with a well‐formed protoplanetary disk. Here, we relax this assumption by modeling the formation and evolution of the solar nebula during and after the period when it accreted material from its parent molecular cloud. We consider how disk building impacts the long‐term evolution of the disk and the implications for grain transport and mixing within it. Our model shows that materials that formed before infall was complete could be preserved in primitive bodies, especially those that accreted in the outer disk. This potentially explains the discovery of refractory objects with low initial 26Al/27Al ratios in comets. Our model also shows that the highest fraction of refractory materials in meteorites formed around the time that infall stopped. Thus, we suggest that the calcium‐aluminum‐rich inclusions in chondrites would be dominated by the population that formed during the transition from class I to class II stage of young stellar objects. This helps us to understand the meaning of t = 0 in solar system chronology. Moreover, our model offers a possible explanation for the existence of isotopic variations observed among refractory materials—that the anomalous materials formed before the collapse of the parent molecular cloud was complete.