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What Are Sunspots?

Credit: NASA
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The Old Farmer's Almanac uses sunspot activity to help in making its weather predictions. What exactly are sunspots?

When the Sun's magnetic field pokes through its surface, it prevents the heat rising inside from coming through. As a result, the Sun's surface at these areas is cooler and darker than its surroundings, although still very bright. These dark areas are called sunspots.

Sometimes, when the magnetic field suddenly breaks around a sunspot, plasma explodes into space. These explosions, called solar flares and coronal mass ejections, can cause magnetic storms that can temporarily knock out Earth's satellites, electricity, and communications, and pose a hazard to astronauts.

Astronomers study sunspots to determine when these magnetic storms will occur. Scientists also examine how sunspots may affect Earth's climate. They look at . . .

Sunspot Size

Some sunspots are as big as Earth, while others are more than ten times that!

Sunspot Number

The count varies; sunspots often appear in groups. We know that sunspot counts generally rise and fall every 11 years on the average.

Life Span

Each sunspot can last from a few hours to a few months.


This is the periodic change in the frequency of sunspots, which usually occurs over about 11 years.

Read about how The Old Farmer's Almanac makes weather predictions.

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