Stargazers in parts of Europe were stunned by an unusual sight on Monday evening: a large, glowing blue spiral in the sky.

A Curious Blue Swirl of Light Captivates Sky Watchers in Europe 0:27 NOW PLAYING 1:07 0:43 14:22 Two Astronauts on an 8-Day Mission That Turned Into a 9-Month Odyssey 2:05 0:36 2:58 1:03 ...