Twenty-one million light years from Earth is M101, also known as the Pinwheel Galaxy. The galaxy is 70 percent bigger than the Milky Way, and lies in the area of the sky that contains Ursa Major, more commonly called the Big Dipper. From end to end, the galaxy is about 170,000 light years across. The above picture, just released from the Chandra X-Ray Observatory, combines data from four of NASA's big telescopes to give a complete picture of the different light wavelengths coming from the spiral.

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Image: NASA.