Animation of a flight towards the Sun, showing sunspots and prominences erupting from its surface. Prominences are loops of plasma in the atmosphere (corona) of the Sun, following the lines of magnetic fields. Some of these can eject huge amounts of material into space, as a coronal mass ejection. Sunspots are dark regions on the Sun's surface, formed when strong magnetic fields isolate a region of plasma, allowing it to cool and appear relatively dark against the hotter surface. They are associated with prominences and flares. The Sun has a cycle of activity that varies over some eleven years, with sunspots and flares increasing in number during active periods, until the magnetic poles of the Sun switch over at the height of activity, leading to a period of quiescence.