Magnetic seismology of interstellar gas clouds: Unveiling a hidden dimension

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Science  11 May 2018:
Vol. 360, Issue 6389, pp. 635-638
DOI: 10.1126/science.aao1185

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A vibrating molecular cloud in three dimensions

Molecular clouds are relatively dense assemblies of interstellar dust and gas (mostly molecular hydrogen) from which stars form. Determining the three-dimensional (3D) morphology of these clouds is difficult because we only see a 2D projection of them onto the sky. While examining far-infrared observations of the nearby Musca cloud, Tritsis and Tassis discovered that the cloud is vibrating with magnetohydrodynamic waves. The pattern of vibrations reveals the 3D structure and shows that Musca is a sheet seen edge-on, not a filament as previously assumed.

Science, this issue p. 635


Stars and planets are formed inside dense interstellar molecular clouds by processes imprinted on the three-dimensional (3D) morphology of the clouds. Determining the 3D structure of interstellar clouds remains challenging because of projection effects and difficulties measuring the extent of the clouds along the line of sight. We report the detection of normal vibrational modes in the isolated interstellar cloud Musca, allowing determination of the 3D physical dimensions of the cloud. We found that Musca is vibrating globally, with the characteristic modes of a sheet viewed edge on, not the characteristics of a filament as previously supposed. We reconstructed the physical properties of Musca through 3D magnetohydrodynamic simulations, reproducing the observed normal modes and confirming a sheetlike morphology.

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