The Webb Telescope's mirrors are coated in an extremely thin film of gold. This gold layer, only a few millionths of an inch thick, enables the mirrors to best reflect the infrared light the telescope seeks. The thinner the layer, the better off the telescope will be — every bit of weight counts when a telescope as big as Webb is being lifted into space by a rocket. Join us at Quantum Coating in New Jersey, where engineers are vaporizing gold to apply a thin, even layer to the telescope's mirrors.
Webb's Primary Mirror: An Overview