Annealing of Silicate Dust by Nebular Shocks at 10 AU
Annealing of Silicate Dust by Nebular Shocks at 10 AU
复制标题
10 天文单位星云激波对硅酸盐尘埃的退火
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
S. Desch
中科院分区：
文献类型：
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作者：
D. Harker;S. Desch
已知星际介质中的硅酸盐尘埃颗粒大部分是无定形的，但在许多长周期彗星和原行星盘中观察到结晶硅酸盐颗粒。将无定形硅酸盐颗粒退火成结晶颗粒需要 ≳1000 K 的温度，但彗星中的尘埃颗粒暴露在如此高的温度下与彗星所经历的普遍低温是不相容的。这导致了模型的提出，其中尘埃颗粒在原太阳附近经过热处理，然后经历相当大的径向传输，直到它们到达长周期彗星起源的气态巨行星区域。相反，我们假设硅酸盐尘埃颗粒是通过重力不稳定性引发的冲击波原位退火的。我们假设冲击速度为 5 km s-1，这是由重力不稳定性驱动的冲击的合理值。我们计算了在 5-10 个天文单位的原行星盘典型条件下微米和亚微米球粒陨石成分的非晶辉石颗粒的峰值温度。我们的结果也适用于球粒状无定形橄榄石晶粒。我们表明，亚微米和微米尺寸的硅酸盐尘埃颗粒可以发生原位热退火，从而消除了大规模径向传输的需要。
Silicate dust grains in the interstellar medium are known to be mostly amorphous, yet crystalline silicate grains have been observed in many long-period comets and in protoplanetary disks. Annealing of amorphous silicate grains into crystalline grains requires temperatures of ≳1000 K, but exposure of dust grains in comets to such high temperatures is incompatible with the generally low temperatures experienced by comets. This has led to the proposal of models in which dust grains were thermally processed near the proto-Sun, then underwent considerable radial transport until they reached the gas giant planet region where the long-period comets originated. We hypothesize instead that silicate dust grains were annealed in situ by shock waves triggered by gravitational instabilities. We assume a shock speed of 5 km s-1, a plausible value for shocks driven by gravitational instabilities. We calculate the peak temperatures of micron and submicron amorphous pyroxene grains of chondritic composition under conditions typical in protoplanetary disks at 5-10 AU. Our results also apply to chondritic amorphous olivine grains. We show that in situ thermal annealing of submicron- and micron-sized silicate dust grains can occur, obviating the need for large-scale radial transport.
影响因子：
3.2
作者：
V. Mannings;A. Boss;S. Russell
通讯作者：
V. Mannings;A. Boss;S. Russell