标题： 猎户座分子云表面的波 显示英文标题

标题： Waves on the surface of the Orion molecular cloud

摘要： 大质量恒星影响它们的母分子云，长期以来人们一直怀疑流体动力学不稳定性的发展可以压缩或分裂云。 识别这些不稳定性已被证明是困难的。 有人提出，细长结构（如“创造之柱”）和其他形状是由于不稳定性造成的，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，迄今为止尚未被观察到。 在这里，我们报告在猎户座分子云表面发现了“波”，这些波出现在大质量恒星形成的地方。 这些波似乎是一种开尔文-赫姆霍兹不稳定性，在星云膨胀过程中出现，当由大质量恒星加热和电离的气体吹过先前存在的分子气体时产生。 显示英文摘要

摘要： 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.