The Spinning Sun

Does the Sun spin?

Galileo Galilei, back in 1612, noticed something interesting about the Sun when he observed its sunspots. Let's see what he discovered.

Data | Compute Rotation | Your & Galileo's Discovery | Other Pages

Collect Your Data

If you haven't already done so, collect solar data for a couple weeks by looking at images from the SOHO spacecraft.

Arrange your copies or drawings of the solar disk and sunspots in order from longest-ago to the present, and flip through them slowly as if they were an animated "flip-book". Are the sunspots permanent, or do they come and go? Do they stay in the same place, or seem to move? If they move, do they move in relatively straight lines or do they wander?

Galileo noticed that the spots seemed to move directly across the disk of the Sun. He thought that, if they were on the surface of the Sun, their movement might indicate that the Sun was rotating. What do you think?

Compute the Sun's Rotation Rate

Let's try to calculate the rotation rate of the Sun:

By Estimating

By Calculating the Spots' Angular Velocity

What Did you Discover?

Would you like to compare your sunspot sketches with those made by Galileo?

Galileo's drawings and animations.

Did Galileo's sunspots move horizontally across the solar disk? Do your sunspots move horizontally across the solar disk? If your pictures differ from Galileo's, why do you think that is?

This page is
Created by Deborah Scherrer