The Sun as studied by the Solar and Heliospheric Observatory, or SOHO. Photo: NASA/ESA

Active region 9169 is the host of the largest sunspot group observed so far during the current solar cycle. On September 20, the sunspot area within the group spanned 2,140 millionths of the visible solar surface, an area a dozen times larger than the entire surface of the Earth!

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.

Right now, the sunspot is near the center of the visible disk of the Sun, rotating towards the right (which in fact means towards west, as seen from the Earth), as it gradually changes appearance.