James Webb Space Telescope (JWST) mirror testing. To align each of these 18 hexagonal mirror segments (made from beryllium and coated with gold), they are mounted to six actuators that can adjust the segment in 5-nanometre steps. The JWST is an infrared telescope that is scheduled to be launched in 2021. 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 in December 2010, at NASA's Goddard Space Flight Center in Greenbelt, Maryland, USA.