Northern Lights

Northern Lights - In the foreground, lights along the northern horizon give an orange cast to the low clouds. But far above the clouds, at altitudes of 50 miles or more, are alluring green and purple hues of the aurora borealis or northern lights, a glow powered by energetic particles at the edge of space. In the background are familiar stars of the northern sky. In particular, that famous celestial kitchen utensil, the Big Dipper (left), and the W-shaped constellation Cassiopeia (right) are easy to spot. Then, just follow the pointer stars of the Big Dipper to Polaris, perhaps the most famous northern light of all. — at lmage Credit: Philippe Moussette/Obs. Mont Cosmos/NASA (Quebec, Canada - July '04).