This video from NASA's Solar Dynamics Observatory tracks five new sunspots as they twist and turn on the Sun's surface. Amazingly, all of these sunspots are bigger than the Earth and have more energy than a million nuclear bombs.
Phil Plait over at Bad Astronomy offers this helpful explanation:
Taken over the course of two weeks (half a rotation of the Sun), you can see them pop up, darken, and grow, and even rotate a bit as the Sun's complex magnetic fields change… and the neatest part to me is the foreshortening they undergo as they approach the east side of the Sun's disk. Amazing!
Sunspots are actually regions of slightly cooler material at the Sun's surface. Hot plasma (ionized gas, stripped of one electron or more) rises from the solar interior, reaches the surface, cools off, and sinks back down. This is called convection, and is the same process you see in a pot of boiling water. But at the surface, the tortured and twisted magnetic field of the Sun can suppress convection, preventing the cooler material from sinking. Since the brightness of the plasma depends on the temperature, this cooler stuff is darker. Boom! Sunspot.
This video tracks the five sunspots as they move about from February 7 to 20 of this year. These sunspots are the same ones that ultimately created a massive X-class flare back on March 15.
Via Bad Astronomy.