Centro de Astrobiología, CSIC/INTA, Carretera de Torrejón a Ajalvir, km 4, 28850 Torrejón de Ardoz, Spain.
Nature. 2010 Aug 19;466(7309):947-9. doi: 10.1038/nature09289.
Massive stars influence their parental molecular cloud, and it has long been suspected that the development of hydrodynamical instabilities can compress or fragment the cloud. Identifying such instabilities has proved difficult. It has been suggested that elongated structures (such as the 'pillars of creation') and other shapes arise because of instabilities, but alternative explanations are available. One key signature of an instability is a wave-like structure in the gas, which has hitherto not been seen. Here we report the presence of 'waves' at the surface of the Orion molecular cloud near where massive stars are forming. The waves seem to be a Kelvin-Helmholtz instability that arises during the expansion of the nebula as gas heated and ionized by massive stars is blown over pre-existing molecular gas.
大质量恒星会对其母体分子云产生影响，长期以来人们一直怀疑流体动力学不稳定性的发展会压缩或分裂云。但要识别出这些不稳定性一直很困难。人们认为，拉长的结构（如“创造之柱”）和其他形状是由于不稳定性而产生的，但也有其他解释。不稳定性的一个关键特征是气体中的波状结构，但迄今为止尚未见到。在这里，我们报告了在猎户座分子云的表面存在“波”的现象，这些波似乎是一种开尔文-亥姆霍兹不稳定性，它是在大质量恒星加热和电离气体膨胀超过预先存在的分子气体时，星云扩张过程中产生的。
