Photo Credit: NASA/Reuters. From Time Magazine’s Amazing Photos of the Sun:

A dense cloud of loop-shaped gas erupts from the Sun’s surface. Solar prominences, as this occurrence is called, can loop thousands of miles into space and can persist in the Sun’s corona for several months. The largest known prominence, an extension over 430,000 miles — roughly equivalent to the star’s radius — was observed in 2010.

(Thanks to Raymundo for the link.)