Astronomers Find ‘Vibrating’ Interstellar Cloud
A team of astronomers from the Australian National University and the University of Crete has determined the 3D structure of the interstellar molecular cloud Musca, and discovered that the cloud is vibrating with magnetohydrodynamic (MHD) waves. The advance not only reveals the true structure of the Musca cloud, but it could also lead to a better understanding of the evolution of interstellar clouds in general, which will help astronomers answer the longstanding question: what determines the number and kind of stars formed in our Milky Way Galaxy?
Astronomical objects are seen in 2D projection on the plane of the sky.
This is particularly problematic for studies of the interstellar medium, because the 3D structure of interstellar clouds encodes information regarding the physical processes that dominate the formation of stars and planets.
In the new study, astronomers Aris Tritsis and Konstantinos Tassis managed to reconstruct the full 3D structure of the Musca cloud (also known as G301.70-7.16 or the Dark Doodad Nebula) — a molecular cloud located in the southern constellation of Musca, 490 to 652 light-years from Earth — thanks to its striations.
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The team showed that these striations (wispy stripe-like patterns) form by the excitation of fast MHD waves — the Musca molecular cloud is vibrating, like a bell ringing after it has been struck.
By analyzing the frequencies of these waves, the astronomers produced a model of the cloud, showing that the cloud is not a long, thin filament as once thought, but rather a vast sheet-like structure.
From the 3D reconstruction, the team was able to determine the density of the Musca cloud.
“With its geometry now determined, the Musca molecular cloud can be used to test theoretical models of interstellar clouds,” Dr. Tritsis and Dr. Tassis said.
The findings were published in the May 11 issue of the journal Science (arXiv.org preprint).
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Aris Tritsis & Konstantinos Tassis. 2018. Magnetic seismology of interstellar gas clouds: Unveiling a hidden dimension. Science 360 (6389): 635-638; doi: 10.1126/science.aao1185