<p>Green<a href="http://science.nationalgeographic.com/science/space/universe/auroras-heavenly-lights/"> auroras</a> illuminate the sky over Whitehorse, in <a href="http://travel.nationalgeographic.com/travel/countries/canada-guide/">Canada</a>'s Yukon Territory, on Monday.</p><p>Such auroral displays are triggered when clouds of charged particles from the sun—known as coronal mass ejections (CMEs)—slam into Earth's magnetic field.</p><p>A "severe" CME hit September 26, sparking auroras at both Poles and inducing light shows visible in five U.S. states, including Michigan, New York, South Dakota, Maine, and Minnesota, according to NASA.</p><p>As solar particles get funneled along Earth's field lines toward the Poles, they collide with molecules in the atmosphere, infusing them with extra energy. The molecules in turn release the energy as light.</p><p>Capturing the above aurora required "a long night of waiting-but the activity picked up," photographer Jonathan Tucker wrote on <a href="http://www.spaceweather.com">SpaceWeather.com</a>.</p><p>(Also see <a href="http://news.nationalgeographic.com/news/2011/09/pictures/110914-auroras-northern-lights-science-space-sun/#/aurora-cme-minnesota_40262_600x450.jpg">"New Aurora Pictures: Sun Storms Trigger Sky Shows."</a>)</p>