Astronomy Picture of the Day

Explanation: Last Thursday evening, stars were not the only lights in Iowa skies. Spectacular northern lights also shone from the heavens, extending across the midwestern USA and other locations not often graced with auroral displays. The wide-ranging auroral activity was triggered as a large solar flare - an energetic cloud of particles blasted outward from the Sun a few days earlier - collided with planet Earth's magnetosphere. Alerted to conditions ripe for aurora, photographer Stan Richard recorded this apparition over Saylorville Lake, near Des Moines, Iowa, USA. While the colorful rays seem to end just above the water, they are actually at altitudes of 100 kilometers or more.