EVOLUTION OF SNOW LINE IN OPTICALLY THICK PROTOPLANETARY DISKS: EFFECTS OF WATER ICE OPACITY AND DUST GRAIN SIZE
EVOLUTION OF SNOW LINE IN OPTICALLY THICK PROTOPLANETARY DISKS: EFFECTS OF WATER ICE OPACITY AND DUST GRAIN SIZE
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DOI：
10.1088/0004-637x/738/2/141
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发表时间：
2011-06
期刊：
影响因子：
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通讯作者：
A. Oka;T. Nakamoto;S. Ida
中科院分区：
文献类型：
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作者：
A. Oka;T. Nakamoto;S. Ida
用数值模拟方法研究了光学厚原行星盘中雪线的演化。采用1+ 1维近似计算了圆盘内的温度和密度，得到了圆盘内的凝冰区域。雪线的迁移是由于圆盘中的质量吸积率（）随时间而减小。使用相同的数值方法，从具有高盘吸积率的早期阶段（yr-1）到具有低盘吸积率的后期阶段（yr-1）进行计算。结果表明，雪线在yr-1时向内移动，而在演变后期，雪线逐渐向外移动。除了硅酸盐不透明度外，还考虑了冰的不透明度。在向内迁移阶段，额外的冰不透明度使雪线与中心星星的距离增加了1.3倍（对于直径为10 μm的尘埃颗粒）和1.6倍（对于直径为100 μm的尘埃颗粒）。当粘滞系数α在0.001-0.1之间，尘埃与气体的质量比大于太阳丰度值的十分之一，尘埃颗粒小于1 mm时，雪线在盘演化过程中不可避免地进入地球轨道内部。在类地行星区，无水微行星的形成在整个盘演化过程中似乎是困难的，这对行星形成理论提出了新的挑战。
Evolution of a snow line in an optically thick protoplanetary disk is investigated with numerical simulations. The ice-condensing region in the disk is obtained by calculating the temperature and the density with the 1+1D approach. The snow line migrates as the mass accretion rate () in the disk decreases with time. Calculations are carried out from an early phase with high disk accretion rates ( yr−1) to a later phase with low disk accretion rates ( yr−1) using the same numerical method. It is found that the snow line moves inward for yr−1, while it gradually moves outward in the later evolution phase with yr−1. In addition to the silicate opacity, the ice opacity is taken into consideration. In the inward migration phase, the additional ice opacity increases the distance of the snow line from the central star by a factor of 1.3 for dust grains ≲ 10 μm in size and of 1.6 for ≳ 100 μm. It is inevitable that the snow line comes inside Earth's orbit in the course of the disk evolution if the viscosity parameter α is in the range 0.001–0.1, the dust-to-gas mass ratio is higher than a tenth of the solar abundance value, and the dust grains are smaller than 1 mm. The formation of water-devoid planetesimals in the terrestrial planet region seems to be difficult throughout the disk evolution, which imposes a new challenge to planet formation theory.