A Cold Triumph

The James Webb Space Telescope, Hubble’s successor, is an infrared telescope. Warm materials glow in the infrared, and for this reason Webb optics have to be kept cold — all the way down to 40 Kelvin (or -233C or -388 F). Unfortunately, our technology doesn’t allow us to polish mirrors while working at 40K. Thus, [...]

Engineers dressed from head to toe to avoid contaminating the Webb mirror pieces with unwanted particles are reflected in the mirror segments.The James Webb Space Telescope, Hubble’s successor, is an infrared telescope. Warm materials glow in the infrared, and for this reason Webb optics have to be kept cold — all the way down to 40 Kelvin (or -233C or -388 F). Unfortunately, our technology doesn’t allow us to polish mirrors while working at 40K. Thus, the conundrum for Webb was that the mirrors had to be polished at ordinary temperatures but still had to be the right shape at 40K. When temperatures change so dramatically, mirrors warp and deform.About 10 years ago, a study took place to select the best material for the Webb mirrors. Instead of glass, we decided to use a substance called Beryllium. We found that by using computer models, ...