In his PhD dissertation Martin Bo Nielsen performs observational studies of rotation in stars like the Sun. The interior rotation in stars is thought to be one of the driving mechanisms of stellar magnetic activity, but until now this mechanism was unconstrained by observational data.

NASA’s Kepler space mission provides high-precision observations of Sun-like stars which allow rotation to be inferred using two independent methods: asteroseismology measures the rotation of the stellar interior, while the brightness variability caused by features on the stellar surface trace the rotation of its outermost layers. By combining these two techniques Martin Bo Nielsen was able to place upper limits on the variation of rotation with depth in five Sun-like stars. These results suggest that the interior of other Sun-like stars also rotate in much the same way as our own Sun.