Gyrochronology Tells You About Sun-like Stars

The technique of gyrochronology includes telling the age of a star using its spin. What the astronomers do to determine the spin of a star is to look for changes in its brightness caused by dark spots known as starspots across the star’s surface. Observation of these starspots allows the astronomers to pinpoint the spin of the star.

Its like watching a a dot on a ball and spinning it. When you see the dot appear you calculate the time it took for the ball to spin around once. That gives you the spin time. Now that the astronomers know the spin of the star they use that data to predict the age of the star. In cases of Sun – like stars the spin in starspots takes about 21 days on average.

The speed of the spin of the also allows the astronomers to know the age of the star. A young star is likely to spin around much faster than an older star whose momentum may not be that much. Think of how a young boy can run around all day without getting tired but an older man will make the same journey at a much slower and sedate pace.