Galileo's Shocking Discovery

The imperfect surface of the moon was probably not as shocking to Galileo as the mutable surface of the Sun. Galileo was a proponent of the Copernican, heliocentric "universe," and even Copernicus stated that the Sun represented all that was Good and perhaps represented God himself. What were these curious blisters on the most perfect celestial body in the universe? And why did they move?