NASA / SCIENCE PHOTO LIBRARY NASA / SCIENCE PHOTO LIBRARY
James Webb Space Telescope (JWST) testing. The telescope's primary mirror is in front of a thermal vacuum chamber. When in the chamber the mirror will undergo tests at -234 degrees Celsius to ensure that the instruments and optics can cope with the temperatures they will encounter in space. The 6.5-metre-diameter mirror is made of beryllium covered with a microscopically thin layer of gold, optimizing the reflecting of infrared light. The JWST is an infrared telescope that is scheduled to be launched in 2018. By using infrared wavelengths, the JWST will be able to see through much of the dust that obscures visible light. It will also study dark matter, thought to form the majority of the matter in the universe. Photographed on 25 May 2017, at NASA's Johnson Space Center, Houston, Texas, USA.
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