This image of the nearby spiral galaxy M101, better known as the Pinwheel Galaxy, is a three-color combination of images from NASA's Galaxy Evolution Explorer (GALEX) spacecraft. The ultraviolet light, seen in blue in the arms of the galaxy, shows young stars (only 10 million years old), while the diffuse green visible light traces stars that have been living for more than 100 years. The red visible light image shows the stars that formed over a billion years ago.
GALEX makes observations at ultraviolet wavelengths to measure the history of star formation in the universe 80 percent of the way back to the Big Bang. GALEX has been awarded a "Best of What's New" award from Popular Science magazine, along with another NASA spacecraft, the Space Infrared Telescope Facility (SIRTF). Photo Credit: NASA
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