Explorer 11 
Several telescopes are operating in space right now. They scan the heavens around the clock, in almost every wavelength of energy. They produce spectacular pictures, and help astronomers solve many mysteries, while discovering new mysteries for them to ponder.
The first satellite designed to study the universe beyond our own solar system was launched 50 years ago today. It was designed to study gamma rays, the most powerful form of energy. Earth's atmosphere absorbs them, so at the time, the gamma-ray sky was a complete mystery.
Explorer 11 weighed just 82 pounds, and its single detector could provide only a rough idea of the direction and timing of a gamma-ray observation. Its tape recorder failed at launch, so most of its observations were lost. And it was placed in a higher-than-planned orbit, which carried it into the radiation belts that surround Earth.
Even so, Explorer 11 made some of the first observations of the gamma-ray sky.
Perhaps most important, it found no evidence to support the Steady State theory, one of the competing ideas of how the universe was born.
The theory says that matter is continuously created and destroyed, keeping the universe at a constant density. If this theory were correct, the universe should be filled with gamma rays produced by the complete destruction of matter. But Explorer 11 found no evidence to support it -- a finding confirmed by later and more powerful gamma-ray observatories in space.
Script by Damond Benningfield, Copyright 2011