How do fogs of molecular gas collapse into the burning balls of hydrogen we call stars? Astronomers want to understand how magnetism, gravity, and turbulence interact to prompt star formation in molecular clouds. The problem? No one knows the size and shape of these clouds because we only see them from one point of view.
Now, a team of researchers has found a new way to reveal the 3D structure of one such cloud—by analyzing how the gas oscillates like sound in an organ pipe.
The team observed Musca, a molecular cloud about 570 light-years from Earth that appears as an elongated filament, using the European Space Agency’s Herschel Space Observatory. Around the denser filament there appear to be striations in the gas that astronomers suspected might be caused by waves propagating through the cloud. By analyzing the spacing of the striations, the team showed that they are caused by oscillations of the cloud at resonant frequencies, known as normal modes, they report today in Science.
By modeling such modes in clouds of various shapes, they found that Musca’s true 3D shape is a large sheet that we have been viewing edge-on. They also calculated its size—roughly 26 light-years long and 20 light-years wide. The team hopes this technique could be used to study many other clouds and so shed light on how these stellar nurseries produce their young.