"Previously, theories describing the formation of the Sun and planets could not explain how the Sun has 99.87% of the mass, yet only 0.54% of the angular momentum in the solar system. In a closed system such as the cloud of gas and dust from which the Sun was formed, mass and angular momentum are both conserved. That conservation would imply that as the mass concentrated in the center of the cloud to form the Sun, it would spin up, much like a skater pulling their arms in. The high speed of rotation predicted by early theories would have flung the proto-Sun apart before it could have formed. However, magnetohydrodynamic effects transfer the Sun's angular momentum into the outer solar system, slowing its rotation." (3)
Any extant companion sub-brown dwarf would provide substantial angular momentum to the solar system, filling in the gap that this MHD effect currently explains away. Bearing in mind how mysterious the dynamics of the Sun remain, there is certainly room for debate on this issue. Furthermore, given the potential link between the magnetospheres of the Sun and a proposed massive companion object, it seems telling indeed that NASA should choose ENLIL as the program's moniker.
Andy Lloyd, 16th July 2013