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Sun with solar flares, illustration.
What Is A Sunspot?
History - Science
Over 2000 years ago, astronomers first began to record blemishes on the face of the sun which they believed were omens of important events. With the invention of the telescope in the 17th century, astronomers were finally able to get a close look at these “sunspots,” with Galileo Galilei using their movements to deduce that the sun was rotating.
Sunspots appear darker than the surrounding areas on the sun because they are thousands of degrees cooler than the rest of the photosphere (the part of the sun we can see). They are formed by strong magnetic fields rising to the sun’s surface, and aside from constantly traveling across the face of the sun, they come and go in 11-year cycles.
Sunspots are the barometer by which we measure the seasons of the sun, and the same magnetic fields that lead to their formation can also release the sun’s fury in the form of solar flares. Such flares are divided into several categories, with M-class and X-class flares having the potential to endanger astronauts and damage power grids on Earth.
The largest solar storm on record happened around Halloween in 2003 when the sun unleashed two X-class flares, but the effects on Earth were relatively minimal. Sweden experienced a temporary power outage, flights traveling over the north pole were forced to reroute, and some satellites in orbit around the sun-facing side of the planet were damaged permanently.