Astronomers captured an image of a gigantic coronal hole hovering over the sun's north pole on July 18, 2013, at 9:06 a.m. EDT. Coronal holes are dark, low density regions of the sun's outermost atmosphere, the corona. They contain little solar material, have lower temperatures, and therefore, appear much darker than their surroundings.
Fuente : http://feeds.sciencedaily.com/~r/sciencedaily/~3/q...
Fuente : http://feeds.sciencedaily.com/~r/sciencedaily/~3/q...