James Webb Space Telescope First Infrared Images of the Unseen Universe
The NASA’s James Webb Space Telescope has revealed first full-color images and spectroscopic data of distant galaxies, looking back to the beginning of the cosmic time.
How James Webb Telescope Works?
James Webb Space Telescope detects young galaxies by observing distant ones, which are over 13 billion light years away from earth. To see such far-off and indistinct objects, a large mirror is needed. In other words, how much detail a telescope can see is related to the size of the mirror area collecting light from the observed object. So the mirror in Webb telescope must have a larger diameter than the former Hubble telescope mirror (Figure 1).
James Webb Telescope Mirrors
Scientists and engineers working on Webb telescope mirrors determined that collecting light of very distant galaxies can be achieved by a 6.5-meter diameter mirror, but constructing such mirror is a challenge even for use on earth. Mirror weight rises with its surface, which is another problem for sending such mirror to the space.
James Webb Telescope Deposition
James Webb mirror consists of 18 hexagonal smaller segments, each with a diameter of about 1.32 meter. This design make it possible to fold the mirror into the rocket while sending to space, and unfold it reaching the destination (Figure 2).
JWST’s mirrors have been coated with a microscopically thin layer of gold, which improves reflection of infrared light from the mirrors. This is the primary wavelength of light this telescope will observe, since infrared light is mainly collected from extremely faint objects in the far space (You can read more about coating here).
After final modifications of the mirror shape at low temperature and polishing mirrors surface by specialists, a layer of gold is deposited on their surface (Figure 3).
Gold Deposition in James Webb
Gold is applied to the mirrors by vacuum vapor deposition (Two types of vapor deposition: physical vapor deposition and chemical vapor deposition). A small quantity of gold (0.12 ounce) is vaporized and deposited on the mirror inside a vacuum chamber and a typical thickness of 100 nanometers of gold is obtained. Also, a thin layer of amorphous SiO2 (glass) is deposited on top of the gold to protect it from scratches, since the gold is pure and thus, very soft (Figure 4).
