Finally providing insights into the spin behavior of Sun-like stars outside our solar system, researchers now report that, much like the Sun, some other solar-type stars spin faster at their equators than at their poles. This keener insight into stellar rotation could inform numerous efforts in stellar astrophysics that rely on an understanding of the physical mechanisms acting in a star. Observations of sunspots on the surface of our Sun demonstrate that the equator rotates 30% faster than the poles. Analysis of the Sun's acoustic oscillations shows that this differential rotation extends deep into the interior. This has led to valuable insights into the Sun's structure and may explain how the solar magnetic field is sustained. However, little is known about rotational characteristics of other Sun-like stars and the methods for investigating the phenomenon are limited. Asteroseismology provides a way to probe internal rotation by measuring the acoustic oscillations of stars. Othman Benomar and colleagues used the Kepler spacecraft to monitor the stellar oscillations of 40 Sun-like stars. Among the resonant frequencies of acoustic waves propagating within stars, Benomar et al. measured combinations that are sensitive to rotation. The results show signatures of differential rotation in some of the stars analyzed; thirteen show significant latitudinal differences in speed. In the stars with the strongest signal, the equators spin nearly twice as fast as their mid-latitudes, the authors report. None of the stars surveyed had the opposite pattern of faster poles than equators. Finally, the latitudinal shear they infer is greater than previously predicted, posing a challenge to theoretical models.
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Journal
Science