One of the more striking, yet underrated, components of the James Webb Space Telescope (JWT) is its enormous sunshield. Since the JWT detects in the infrared spectrum, it needs to be incredibly cold, operating at less than -220° C. The sunshield accomodates this by providing an SPF of 1 million, which results in just over a 300° C reduction in temperature between the hot and cold side of the shield – over a thickness of just 4.8 metres!

Source: one