The Webb Telescope Has the Largest Mirror Ever Launched Into Space

A telescope’s power depends heavily on the size of its mirror. NASA states that the primary mirror of the James Webb Space Telescope is 6.5 meters, or 21 feet 4 inches, across, and that it is the largest ever launched into space. Engineers determined that this size was needed to measure the light from extremely distant galaxies. A mirror that big created a problem, because it is larger than the diameter of the rocket that carried it. NASA explains that the mirror is therefore segmented and designed to fold for launch. It is made of 18 hexagonal segments, each 1.32 meters across. The segments are made of beryllium, and each has a very thin coating of gold, which improves the mirror’s reflection of infrared light.