Two astronomers determine the 3D structure of the Musca cloud for the first time. The breakthrough step could yield more clues of how exactly stars are formed.

The map reveals that the molecular cloud Musca is actually shaped like a pancake despite previous studies saying that Musca is shaped like a needle. With this discovery of its actual shape, the astronomers were also able to study how forces acted on Musca for it to process the creation of stars.

Musca lies in the Southern Hemisphere about 500 light-years away from Earth, which is why charting its shape had been challenging for scientists. In general, 3D construction of interstellar clouds or practically all astronomical bodies can only be observed through infrared or 2D projections — that is, until this study.

The Song

For their study, the astronomers specifically chose Musca because its "song" or vibration was unlikely to be affected by other sounds coming from nearby bodies since it was an extremely thin cloud — or so they thought.

Aris Tritsis, lead author of the study from the University of Crete, and Konstantinos Tassis, senior author and an astrophysicist from the same university, were able to create the full 3D structure of Musca by observing its striations or the translucent patterns made as it moves. These patterns are formed when fast magnetosonic waves or longitudinal magnetic pressure waves were applied.

They found that Musca cloud is vibrating, similar to a bell ringing after it has been struck.

"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," the authors write in the study published in the journal Science. It was a pancake-shaped cloud and not a needle-shaped cloud.

With the discovery of its actual shape, the astronomers also gathered that Musca cloud has a lower density than previously thought, which also means that stars formed through it have a different composition.

The denser clouds are potentially made up of nitrogen-based molecules such as ammonia, Tassis explains. Also, cloud with less density creates stars at a much lower rate compared with denser clouds.

Pancake Shape

There is a big difference between pancake-like clouds and needle-like clouds.

"Magnetic forces make pancake-like clouds, turbulence forms needle-like clouds and thermal forces result in roundish, bobby clouds," Tassis explained.

With the precedence set by their study, other scientists have a lower chance of mistaking pancake-shaped clouds from the needle-shaped ones which means they could study more accurately what kind of forces clouds use to form the stars. In the case of Musca, it uses magnetic forces to create stars.

Tritsis and Tassis said that with the 3D image of Musca, the cloud can be used to test future theoretical models of more interstellar clouds.

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