Astronomy Picture of the Day

Explanation: It looks like a fine collection of aggies. But this grid of embedded swirls and streaks actually follows the dramatic development of planet Earth's auroral substorms. The sequence of over 600 horizon-to-horizon fisheye images was taken over a 2 hour period near the artic circle in March of 2012 from Lapland, northern Sweden. It begins at upper left in evening twilight and ends at lower right, covering two activity peaks with bright coronae forming overhead. While exploring space between Earth and Moon, NASA's fleet of THEMIS spacecraft discovered that these explosions of auroral activity are driven by sudden releases of energy in the Earth's magnetosphere. Even if you're not playing for keepsies, you can follow this link to check out the sequence in a full timelapse video (vimeo).