Solar Cycle

Science • Space
Solar Cycle 25 has begun
This split image shows the difference between an active Sun during solar maximum (on the left, captured in April 2014) and a quiet Sun during solar minimum (on the right, captured in December 2019).
This split image shows the difference between an active Sun during solar maximum (on the left, captured in April 2014) and a quiet Sun during solar minimum (on the right, captured in December 2019). Credit: NASA/SDO

The sun is starting over. NASA reports that Solar Cycle 25 has begun in December 2019, signaling an increase in space weather that could impact the Earth's power grid, airlines and astronauts in space. Roughly every 11 years, the sun completes a solar cycle of various activity measures in the number of sunspots on the solar surface.

"As we emerge from solar minimum and approach Cycle 25’s maximum, it is important to remember solar activity never stops; it changes form as the pendulum swings," said Lika Guhathakurta, solar scientist at the Heliophysics Division at NASA Headquarters in Washington.