Magneto-Centrifugal Origin for Protostellar Jets Validated through Detection of Radial Flow at the Jet Base

Jets can facilitate the mass accretion onto the protostars in star formation. They are believed to be launched from accretion disks around the protostars by magneto-centrifugal force, as supported by the detections of rotation and magnetic field in some of them. Here we report a radial flow of the textbook-case protostellar jet HH 212 at the base to further support this jet-launching scenario. This radial flow validates a central prediction of the magneto-centrifugal theory of jet formation and collimation, namely, the jet is the densest part of a wide-angle wind that flows radially outward at distances far from the (small, sub-au) launching region. Additional evidence for the radially flowing wide-angle component comes from its ability to reproduce the structure and kinematics of the shells detected around the HH 212 jet. This component, which can transport material from inner to outer disk, could account for the chondrules and Ca-Al-rich inclusions detected in the Solar System at large distances.