A close-up of sunspots. Credit: SOHO (NASA & ESA) and the Royal Swedish Academy of Sciences
We use satellites to monitor sunspots and their magnetic activity, which can tell us where the sun is in the solar cycle and how much activity we can expect in the future.
What Exactly Are Sunspots?
Sunspots are cooler, darker regions of the sun’s surface that form when magnetic fields are twisted and stretched. When this happens, the magnetic activity can become so strong that it prevents the flow of heat, lowering the temperature in that area. Sunspots can be ~3000 Fahrenheit (~1650 Celsius) cooler than the area around them, which makes them appear dark. The average sunspot is roughly the same size as Earth.
Humans used telescopes to observe sunspots as early as the 17th century. While satellites are now the primary tool used for studying the sun, ground-based observations are still used to track sunspots.
How Sunspots Fit Into the Solar Cycle
Although the sun may look like a constant ball of light every day, its activity rises and falls in a repeating cycle of about 11 years. A period of low activity, or solar minimum, in 2019 marked the beginning of solar cycle 25. In 2024, it entered into solar maximum, which is the peak of activity in the cycle. It will end when the next solar minimum is declared, completing the ~11-year wave. As solar activity increases, so does the likelihood of stronger solar storms.
The number and location of sunspots change with the solar cycle. During solar maximum, there are a high number of sunspots, and during solar minimum, there are a low number of sunspots or none at all. Sunspots appear in a wide variety of shapes and sizes, can change over time, and may last anywhere from a few hours to several months.
