You are looking at the sun, imaged in extreme ultraviolet light (invisible to us) and shown in false color. To learn more about the sun, visit this this National Geographic article, and also this Hyperphysics page.
Notice how irregular the edge of the sun looks. Hot matter streams from the surface and returns, or occasionally some breaks off and heads out into the solar system. See From Physics Research for more information on this matter and how it moves.
