凍結線 (天文學)




凍結線（英语：Frost line），又譯為雪線（英语：Snow line）或冰線（英语：Ice line），在天文學或行星科學中，是指能讓揮發物質（如水、氨和甲烷等物質）凝聚為固體冰粒的最小距離（由母恆星中心起算），這個名詞是借用土壤學中凍線的概念。就太陽系而言，凍結線位於太陽星雲中從原始太陽的中心向外起算的一個特定距離，此處的溫度一般認為介於 140[1] 至 170 K[2] 之間。


由於採用的物理模型和計算方式對於計算凍結線距離有很大的影響，通常很難得出凍結線的確切距離。就太陽系而言，綜觀迄今所被提出過的所有理論值，太陽系的凍結線主要被認為落在 2.7[2] 至 5 AU[3] 之間，亦即火星與木星間的主小行星帶。溫度在凍結線之下的低溫能讓更多的固體顆粒吸積成為微行星，最終能成為行星。因此，凍結線將恆星系劃分為擁有固態物體但揮發性物質稀少的類地行星區域，以及富含揮發性物質與冰冷物體的類木行星區域[4]。



參考文獻





  1. ^ Podolak, M.; Zucker, S. A note on the snow line in protostellar accretion disks. Meteoritics & Planetary Science. 2004, 39 (11): 1859–1868. Bibcode:2004M&PS...39.1859P. ISSN 1086-9379. doi:10.1111/j.1945-5100.2004.tb00081.x. 


  2. ^ 2.02.1 Hayashi, C. Structure of the Solar Nebula, Growth and Decay of Magnetic Fields and Effects of Magnetic and Turbulent Viscosities on the Nebula. Progress of Theoretical Physics Supplement. 1981, 70: 35–53. ISSN 0375-9687. doi:10.1143/PTPS.70.35. 


  3. ^ Jewitt, D; Chizmadia, L.; Grimm, R.; Prialnik, D. Water in the Small Bodies of the Solar System. (编) Reipurth, B.; Jewitt, D.; Keil, K. Protostars and Planets V (PDF). University of Arizona Press. 2007: 863–878. ISBN 0-8165-2654-0. 


  4. ^ 林潮（David N. C. Lin）. 行星創世紀（The Genesis of Planets）. 科學人中文版. 2008年6月, 76. ISSN 1682-2811. 




相關條目




  • 太陽星雲學說

  • 太陽系的形成與演化




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