The Solar Rotation Period

The first measurements of the period for solar rotation were made by tracking sunspots as they appeared to move around the Sun. Galileo used this method to deduce that the Sun had a rotational period of about a month.

Because the Sun is not a solid body, it does not have a well-defined period for rotation. Modern data indicate that the rotational period of the Sun is about 25 days near its equator, 28 days at 40 degrees latitude, and 36 days near the poles. The rotation is direct, that is, in the same sense as the motion of the planets around the Sun.