9. Sunspots at Solar Maximum and Minimum (March 20, 2009)
It's been quiet lately on the sun, as seen in the two right-hand images. The normally stormy star is in a period of solar minimum, with fewer sunspots in 2008 than have been observed since 1957. But nine years ago the sun was vomiting intense magnetic activity and solar flares, as seen in the left-hand solar maximum images.
The top row of images depicts the sun as observed in visible light by the SOHO spacecraft, while the bottom row uses the same craft's Extreme Ultraviolet Imaging Telescope to capture solar flares.
Severe space weather, such as that shown in the left-hand images, poses a threat to humans' high-tech infrastructure, damaging electronic and electrical equipment.
Images by SOHO, the EIT Consortium, and the MDI Team, courtesy Earth Observatory