Kyoto, Japan -- From birth to death, stars generally slow by 100 to 1000 times their initial rotation rates; in other words, they spin down. The Sun's total angular momentum has declined as material is gradually blown off at the surface as solar wind. By observing this, astronomers have theorized the interaction between magnetic fields and plasma flow to be the most efficient way to spin down stars.

Why and how this happens has long interested astronomers, and recently an observational technique called astroseismology, which measures a star's natural oscillation frequencies, has made it possible to measure the internal rotation rates and magnetic fields of other stars in our galaxy. From this huge population, a picture of how stellar rotation decreases with stellar age has emerged, one that suggests that current theory is insufficient to explain the dramatic decrease in rotation.

Fascinated by astroseismology and by other researchers' 3D simulations of the solar convective zone, a team of researchers at Kyoto University was inspired to investigate how magnetic fields affect rotation inside massive stars..