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The Sun has been steadily burning hydrogen into helium for billions of years. It’s been around for 4.6 billion years, and will continue on for another 7 billion years or so as a main sequence star. But if you take a close look at the Sun, you’ll see that the activity rises and falls over the course of an 11-year cycle. There can be many sunspots, which decrease to almost zero and then return 11 years later when there can be dozens across its surface. When the sunspot number is at its greatest, astronomers call this the solar maximum (or solar max).
Solar astronomers are still trying to understand exactly how the Sun’s cycle works, but it all comes down to the Sun’s magnetic field. Over the course of the full 22-year cycle, the Sun’s magnetic field twists up and then shifts polarity. Its north pole becomes its south pole and vice versa. It takes 22 years for the polarity to return to its original configuration.
Sunspots are regions on the Sun’s surface where the temperature is slightly lower than the surroundings. They’re the spots on the Sun’s surface where the Sun’s magnetic field pierces the surface of the Sun.
During the solar maximum, the Sun’s surface around its equator has many sunspots. In addition to all the sunspots, there is a tremendous amount of solar activity. Powerful X-ray flares flash from the surface of the Sun, and coronal mass ejections can blast energy and particles into space. During the solar maximum, we experience more vivid Northern Lights.
The last solar maximum occurred back in the year 2001. And so the next peak is expected to be sometime in 2012.
We have written many articles about the solar maximum on Universe Today. For example, the prediction that the next solar max will be a big one. And even though the next peak is due for 2012, there won’t be a killer solar flare.
Here’s a website dedicated to solar cycle 24.
We have recorded an episode of Astronomy Cast just about the Sun called The Sun, Spots and All.