A mirror for different light
The James Webb Space Telescope observes the universe in infrared light. Its mirror coating was chosen for that task: NASA explains that gold reflects infrared light particularly well. Light reflected towards the instruments can contribute to an image or spectrum; light absorbed by the mirror cannot. The golden surface is therefore part of the observatory’s optical design. It is not a decorative flourish or a statement about the financial value of the spacecraft, and its purpose depends on the wavelengths being observed. [1]
Gold at the surface
The mirror structure beneath that coating is beryllium, selected for a combination of strength, low weight and stability at low temperatures. NASA describes a gold coating approximately 100 nanometres thick, deposited after the mirror has been shaped and polished. A protective glass layer lies above it. Structure and surface thus perform different jobs: the supporting material preserves the required shape, while the coating helps determine how light is reflected. Calling the mirrors solid gold would miss that division of labour. [1] [2]
A golden blanket may be something else
Spacecraft photographs often show crinkled, gold-coloured insulation, but appearance is not a reliable material label. NOAA explains that multilayer insulation commonly uses polymer films with thin aluminium coatings; the outer polyimide can give a golden appearance. Webb’s sunshield is another distinct system: NASA describes Kapton membranes with aluminium coatings and additional treated-silicon coatings on specified surfaces. The mirror, sunshield and spacecraft insulation have different functions and constructions. A shared colour does not make them the same material. [3] [4]
A precious metal becomes an engineering material
The telescope brings the collection back to a recurring idea: gold’s usefulness depends on context. A bullion bar concentrates value in a convenient object; an optical coating puts a small amount of metal precisely where its surface properties matter. Neither application explains all of gold’s roles. Looking beyond the colour reveals the engineering choices—wavelength, supporting structure, temperature and protection—that turn a familiar substance into part of a scientific instrument capable of studying an unfamiliar universe. [1] [2]
Sources & further reading
- NASA · Webb Telescope Overview ↗
- NASA · Webb’s Mirrors ↗
- NOAA · Are Satellites Covered in Gold Foil? ↗
- NASA · Sunshield Membrane Coatings ↗
Sources checked 14 November 2026. The artwork is illustrative. Reference organisations do not endorse this website. Financial examples are educational, not investment recommendations.