Answer:
According to Galileo's observations, the rotation period of the Sun was approximately 25-26 days. Galileo made these observations by studying sunspots, which are darker regions on the surface of the Sun. He observed that sunspots appeared to move across the surface of the Sun, completing one full rotation approximately every 25-26 days. This was one of the first indications that the Sun rotates on its axis, and helped to lay the foundation for our understanding of the internal structure and behavior of the Sun.