Coupling of the magnetic field and rotation in the dark cloud B5

We present observations which indicate that the central region of the dark cloud B5 is rotating in the opposite sense to that of the bulk of this approx.300 M/sub sun/ region. The direction of elongation of the cloud coincides with its axis of rotation; both are perpendicular to the galactic plane and to the direction of the magnetic field in the region. This configuration, together with the unusual rotation curve of the cloud, suggests that magnetic braking has played an important role in its dynamical evolution. The retrograde motion of the core relative to the bulk of the cloud is explainable if significant angular momentum transfer has taken place by means of a frozen-in magnetic field