Astronomy Picture of the Day

Explanation: Sailing upside down, 115 nautical miles above Earth, the crew of the Space Shuttle Endeavour made this spectacular time exposure of the southern aurora (aurora australis) in October of 1994. Aurora, also known as the northern and southern lights, appear as luminous bands or streamers of light which can extend to altitudes of 200 miles. They are typically visible from the Earth's surface at high latitudes and are triggered by high energy particles from the Sun. The delicate colours are caused by energetic electrons colliding with oxygen and nitrogen molecules in the upper atmosphere. In this picture, the rear structure of the shuttle Endeavour is in the foreground with the vertical tail fin pointed toward Earth. Star trails are the short streaks above Earth's horizon.