 The James Webb Space Telescope will have 18 hexagonal beryllium sections for its mirrors . Because JWST will face a temperature of 33 K , the mirror is made of gold @-@ plated beryllium , capable of handling extreme cold better than glass . Beryllium contracts and deforms less than glass – and remains more uniform – in such temperatures . For the same reason , the optics of the Spitzer Space Telescope are entirely built of beryllium metal . 
