We might like to think of the Sun as a steady, calm source of light and heat, but in reality it undergoes a cycle of violent activity driven by magnetic fields. This cycle peaks every 11 years or so, and we're due for the next maximum in 2013 or 2014. The previous minimum lasted an unusually long time, but things started ramping up again in 2011. Sunspots marring the Sun's face started appearing in greater numbers, and many of them were the source of incredible outbursts of energy called solar flares.

This picture shows a flare from August 2011, as seen in the ultraviolet by NASA's Solar Dynamics Observatory. When the subatomic particles spurted out by such flares interact with our own magnetic field, the result can be spectacular aurorae, which are also becoming a common sight. They can also cause blackouts (as a particularly large event did to Quebec in March 1989) and damage our satellites - including GPS and communication satellites. Studying the Sun is more than just science: our economy can literally depend on it.

Image credit: NASA/SDO/AIA

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