The Solar and Heliospheric Observatory (SOHO) has been watching the Sun for almost 20 years. In that time it has seen solar activity ramp up and die down repeatedly. Its Extreme ultraviolet Imaging Telescope has taken images of the resulting waxing and waning of the Sun’s corona – its atmosphere – that are impossible to record from the ground.
Brighter images show times when there was more activity on the Sun. This activity is driven by the Sun’s magnetic field and follows a cycle of about 11 years.
credit: SOHO (ESA&NASA)