May 22, 2009--A still from video taken by NASA's STEREO probe shows a solar prominence that seemed to somersault as it rose high into the sun's atmosphere on May 15.

Prominences are loops or streams of relatively cool, dense gas that erupt from the sun's surface and can extend hundreds of thousands of kilometers into space. Astronomers are not yet sure what drives prominences, although they suspect the sun's magnetic activity may be involved.