The Sun

NASA explains solar cycle 25

What does a solar cycle mean for Earth?

Originally Published: 

In September 2020, NASA announced that the Sun had entered its 25th solar cycle since recording began in 1755.


These cycles last about 11 years, and come with a solar minimum and a solar maximum. This year’s solar maximum may arrive by 2025, solar physicists say.

So what does this even mean?

The Sun goes through these cycles as its magnetic field switches — the north pole becomes the south, the south pole becomes the north.

And as this magnetic field shifting occurs, the Sun’s activity increases or decreases.

That means the Sun could produce more solar flares, huge events that project radiation into space, or more frequently hurl huge bubbles of plasma and radiation into space as coronal mass ejections.



These events, if directed at Earth, could disrupt our radio communications, GPS signals, and power grids.

Solar activity is measured by counting sunspots — dark spots on the Sun where pockets of magnetic field are so strong they block super heated material from reaching the Sun’s surface. More sunspots means a more active Sun.


Scientists study the Sun’s solar cycle to better predict space weather, which results from solar eruptions.


Space weather can affect not just our communications on Earth, but also astronauts in the International Space Station.

So scientists study solar cycles, and the activity that comes with, to be better able to protect astronauts in space.



One day, humanity may send astronauts back to the Moon and onward to Mars — and we’ll need to protect them from violent eruptions from the Sun.

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