The northern lights dance over the Knik River near Palmer, Alaska. Activity on the surface of the sun creates this natural light show, but severe solar storms could devastate Earth's power and water utilities, and knock out communications.
Taken in 1990 by NASA's Voyager 1 spacecraft, the "pale blue dot" photo shows what our planet looks like from 4 billion miles away. Earth is the tiny speck of light indicated by the arrow and enlarged in the upper left-hand corner. The pale streak over Earth is an artifact of sunlight scattering in the camera's optics.
The 12-inch gold-plated records contain greetings in 59 languages, samples of music from different cultures and eras, and natural and human-made sounds from Earth. One record is currently 16.89 billion km from Earth, the other is over 13 billion km away.
NASA Center: Jet Propulsion Laboratory
Coronal loops, seen here, are fountains of multimillion-degree gas in the atmosphere of the sun. They are often precursors to solar flares, which emit strong bursts of electromagnetic energy.
The space shuttle Discovery orbits in space in a March, 2009 mission. The nearly 30-year-old space shuttle program is set to end in 2010. After five more missions, NASA's three shuttles — the Discovery, Atlantis and Endeavour – will be retired.