Why Stars Spin Up (or Down) Before They Die

Posted by Guy Pirro | 06/17/2026 01:40AM | Comments

From birth to death, stars generally slow by 100 to 1000 times their initial rotation rates. In other words, they spin down. Astronomers at Kyoto University in Japan have theorized that the interaction between magnetic fields and plasma flow may be the most efficient way to spin down stars. Why and how this happens has long interested astronomers, and recently an observational technique that measures a star's natural oscillation frequencies has made it possible to measure the internal rotation rates and magnetic fields of 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 decreases in rotation that have been observed.