Final answer:
Galileo Galilei's discovery of sunspots revealed that the Sun is not a perfect, unchanging sphere but undergoes constant change, with spots being cooler and thus darker regions. Sunspot cycles were later identified by Heinrich Schwabe, demonstrating systematic changes in sunspot numbers over approximately a decade.
Step-by-step explanation:
Galileo's discovery that the Sun has "blemishes," known as sunspots, marked a significant shift in our understanding of our closest star.
These sunspots are large, dark areas on the Sun's surface that appear darker due to being cooler than the surrounding areas—they are at about 3800 K compared to the surrounding 5800 K. Through his observations with the telescope, Galileo began to unravel the mysteries of our celestial neighbors, leading to a greater understanding of the perpetual state of change the Sun experiences. This knowledge has immense implications, as activities on the Sun, such as giant explosions and the sunspot cycle, can impact Earth in various ways, such as causing power outages due to charged particles and energy released from the Sun.
It was Heinrich Schwabe, an amateur astronomer, who through persistent observation discovered the sunspot cycle, revealing a systematic variation in the number of sunspots with a period of about a decade. Together, these discoveries have deepened our understanding of the dynamic nature of the Sun and its effects on the Solar System.