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.
Or, in this case, sunspots. You can see five of the suckers here, changing and mutating as the plasma interacts with the magnetic field. I recognize these spots, too: they were responsible for the first X-class flare of the season on March 15th. There’s dramatic footage of that as well which I posted on my blog at the time. They’re busy spots; they blew out a lower energy flare a few days earlier, too.
And here I am calling them cute and little when they’re actually comfortably bigger than the Earth and exploded with the energy equivalent of millions — millions! — of nuclear bombs.
Now I'm excited, too! Watch the video at Bad Astronomy. Link
(Image credit: NASA/SDO)