How stars spin
doi:10.1038/nindia.2012.126 Published online 31 August 2012
Astrophysicists have got new insights into the rotation of an early red-giant star (KIC7341231) about its axis. This may throw new light on star and planet formation since such rotation results in a mixing of the chemical elements inside stars.
Red-giant stars are towards the end of their life, burning hydrogen fuel with great luminosity. Using observational data and theoretical models, the researchers detected differential rotation, with the core region of the star rotating faster than the surface.
Rotation occurs due to the angular momentum of a star, playing a central role in star and planet formation. Most of the observational data are limited to surface rotation. Despite its importance, very little is currently known about the internal rotation of stars beyond the discovery of differential rotation between the core and surface regions of the Sun, which is predicted to evolve into a red giant.
To find new aspects of a star's internal rotation, the researchers observed the early red-giant star (KIC7341231) using the electronic gaze of Kepler spacecraft. In addition, they analysed the rotation with the help of theoretical models.
The researchers detected mixed modes of rotation in the spectrum of the red-giant star during observation with the spacecraft.
By analysing the oscillation spectrum of the star, they precisely identified rotational splitting of 18 modes with distinct differences in modes of rotation between the core and surface. The core region was found to spin at least five times faster than the surface.
The researchers say that they plan to detect similar rotational phenomena in other red giant stars. The internal rotation of those stars can be inferred by interpreting the mixed modes of rotation.