Chaotic magnetic fields pose no obstacle to star birth 

Chaotic magnetic fields pose no obstacle to star birth 

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Have you ever seen how a magnet creates patterns in a sprinkling of iron filings? Every material that conducts electricity (like iron) responds to magnetic forces. In the universe, magnetic fields are important, too. They strongly influence the motions of gas particles. Little wonder then that magnetic fields also play a role in the formation of stars. After all, stars are born in contracting clouds of gas and dust. Such clouds often contain magnetic fields. 

In the past, astronomers believed that a strong, orderly magnetic field would help in the formation of new stars. The strong field would funnel gas to regions of higher density – high enough for a star to be born. In contrast, chaotic magnetic fields would probably inhibit star formation, it was thought. But new ALMA observations now reveal that stars can also form in regions with weak chaotic magnetic fields. 

ALMA is able to study magnetic fields by measuring the so-called polarization of millimeter radiation from dust particles. These particles are often elongated, and they get aligned by magnetic forces, just like particles of iron filing. The alignment shows up in the millimeter 

radiation observed by ALMA. The millimeter waves oscillate more strongly in one direction than in other directions – an effect known as polarization. 

Astronomers studied the polarization of millimeter radiation from dust surrounding a very young baby star. The observed polarization tells them that the magnetic field close to the newborn star is both weak and chaotic. Apparently, chaotic magnetic fields – and the accompanying turbulent motion of gas and dusts – are no obstacle in the formation of new stars. 

The new ALMA result reveals that stars can form under very different circumstances. With more observations, it will be possible to tell which situation occurs more often: strong, ordered magnetic fields or weak, chaotic fields. 


ALMA was used to study a young ‘protostar’ – a star that is still in the process of being born. The star is known as Ser-emb 8. It is located in a star-forming region in the constellation Serpens (the Snake), at a distance of 1400 light-years. By studying the polarization of the millimeter radiation from dust particles surrounding the protostar, it was possible to learn about the strength and the orientation of the magnetic fields in the dust. 


The protostar was observed by an international group of astronomers from the United States, Spain, Chile, Germany, and Taiwan. The research was led by Charles Hull of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. The results have been published in Astrophysical Journal Letters.