Massive stars influence their parental molecular cloud, and it has long been suspected that the development of hydrodynamical instabilities can compress or fragment the cloud1,2. Identifying such instabilities has proved difficult. It has been suggested that elongated structures (such as the ‘pillars of creation’3) and other shapes arise because of instabilities4,5, but alternative explanations are available6,7. 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.
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We thank J. Bally and M. Pound for their comments, which contributed to the improvement of the manuscript. We also acknowledge B. Lefloc’h, J. Goicoechea and J. Martín-Pintado for discussions. D. Hochberg is acknowledged for his reading of the manuscript. O.B. acknowledges C. Joblin for support. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA.
The authors declare no competing financial interests.
This file contains Supplementary Data, Supplementary Figures 1-2 with legends and References. (PDF 290 kb)
This video shows the CO emission of the Orion cloud at all velocities observed with the IRAM 30m telescope. The KH arrow shows the position of the waves. (MP4 1039 kb)
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Berné, O., Marcelino, N. & Cernicharo, J. Waves on the surface of the Orion molecular cloud. Nature 466, 947–949 (2010). https://doi.org/10.1038/nature09289
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