Compare this true-color image of the sun with an image of the sun taken in ultraviolet light (middle). The bright spots in this image show regions of increased activity.   And in X-ray light (bottom)we see regions of the sun that are physically quite different. X-ray light is produced by very fast moving, hot gas, such as in the outer atmosphere of the sun called the corona. The corona is normally invisible to us, but using the light of X-rays, we can see this ultra-hot gas and study how it changes in time. The dark areas are where the sun has recently blasted off some of its surface material, literally punching holes in the corona.