Astronomers Find Super-Fast Rotation of Baby Star’s Jet

ALMA observations of protostar FIR 6B revealed that fast-rotating jets powered by magnetic fields play a critical role in helping young stars grow.

It is known that gas jets are ejected from a baby star, but it was not clear how the jets are formed. By observing the rotation of the jets in detail and combining it with theoretical models, astronomers identified the driving mechanism and the role of the jets in star formation.

Using ALMA, the team led by Yuko Matsushita at NAOJ found that the jets from a protostar OMC 2/FIR 6B are rotating at very high speed. The velocity of rotation and angular momentum of the FIR 6B jets are the highest among all the jets detected so far. The rotational velocity and angular momentum are much larger than previously predicted and can only be explained by the magnetic drive model. The rotation of the jet can be realized by forcing the rotation of a disk at a radius of 3 au from the protostar to be transmitted to matter at a distance of 100 au by the force of a magnetic field.

This research has also clarified that jets appear due to the effect of magnetic fields. The jet also causes the gas in the disk to lose its angular momentum and fall to the center of the disk, helping the protostar to grow.

These super-fast rotating jets appear only during the short period when the young star growing. This study showed that jets play an essential role in the growth of stars.

Reference: “Super-fast Rotation in the OMC 2/FIR 6b Jet” by Yuko Matsushita, Satoko Takahashi, Shun Ishii, Kohji Tomisaka, Paul T. P. Ho, John M. Carpenter and Masahiro N. Machida, 22 July 2021, The Astrophysical Journal.
DOI: 10.3847/1538-4357/ac069f

This research was supported by JSPS KAKENHI (No. JP21K03617, JP21H00046).

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