Day Lab Part 3: Rotational Period of the Sun

The motion of the sun in the sky tells us something about the rotation of the Earth, and the Earth's orbit around the Sun. An important motion of the sun itself is its rotation about its own axis. This can be measured by using sunspots as tracers of that rotation, as Galileo first did in 1612. 

By capturing images of the sun over time, we can use distinct sun spots to follow the rate of its rotation, or its rotational period. To do this, we used images of the sun, and laid a transparency over each image, marking distinct sunspots on a coordinate system. Below is an image of the sun with the overlaid transparency.

After marking the spots, we then removed the transparency, and collected the data on how many degrees each spot moved.

Finally, we used the data and generated average rotational rates for each spot.

To arrive at our final number, we averaged the three values from each sun spot to get an average rotation of 27.57 earth days per rotation.