2009MNRAS.395L..81B

Only a few molecular clouds in the solar neighbourhood exhibit the formation of only low-mass stars. Traditionally, these clouds have been assumed to be supported against more vigorous collapse by magnetic fields. The existence of strong magnetic fields in molecular clouds, however, poses serious problems for the formation of stars and of the clouds themselves. In this Letter, we review the three-dimensional structure and kinematics of Taurus - the archetype of a region forming only low-mass stars - as well as its orientation within the Milky Way. We conclude that the particularly low star formation efficiency in Taurus may naturally be explained by tidal forces from the Galaxy, with no need for magnetic regulation or stellar feedback.