Galileo made a series of sunspot drawings in
the summer of 1612. The drawings are particularly illustrative
when viewed in sequence because they were made at approximately
the same time of day. The 36 drawings illustrate the motion
of sunspots across the diskwhich
is actually a sequence showing the rotation of the Sun. The
changes in the sunspot groups and sizes can also be observed.
The equator and rotation axis of the Sun can be determined
after watching the direction of the sunspots over time. The
images are taken from Professor Owen Gingerich's copy of the
first edition of Galileo's Istoria e dimostrazioni intorno
alle macchie solari e loro accidenti (History and Demonstrations
Concerning Sunspots and Their Properties), published in 1613.
See more of Galileo's
Sunspot drawings on the Rice University Web site.
Learn more about Sunspots
on the Exploratorium's Sunspot Web site.