File:Sunspots on sun.jpg

Image of the sun's solar disk, showing sunpsots on the surface.

Source (Wikipedia): Image:Sunspot with Earth Comparison.jpg (excerpt extracted for just solar-disk image).

Variations:
 * with closeup of upper sunspots: Image:Sunspot with Earth Comparison.jpg.

Explanation
The top group of sunspots is active region 9393, as seen by the MDI instrument on SOHO, which was the largest sunspot group observed so far during the current solar cycle. On 30 March 2001, the sunspot area within the group spanned an area more than 13 times the entire surface of the Earth. It was the source of numerous flares and coronal mass ejections, including one of the largest flares recorded in 25 years on 2 April 2001. Caused by intense magnetic fields emerging from the interior, a sunspot appears to be dark only when contrasted against the rest of the solar surface, because it is slightly cooler than the unmarked regions. The image was created by NASA, an agency of the US Federal Government.