The new mirror is as revolutionary as the spacecraft that carries it. Instead of being in a single piece, it is made of 18 gold-plated beryllium hexagonal mirror segments measuring 1.32 m (4 ft). These are controlled by hundreds of actuators that allow the telescope to adjust its own optics. This is extremely important because the JWST will be over a million miles away. The Hubble mission's early days were marred by a design flaw that required astronauts to visit the telescope several times to make repairs and adjustments, but this won't be an option for the JWST – it has to be as self-reliant as possible.

Unlike the Hubble, which sees in visible and ultraviolet light, the JWST looks in the infrared range. This will allow it to see further into the past than any previous instrument by seeking out objects at the edges of the universe, which date back to near the beginning of time and are receding from us so fast that their light has shifted into the infrared band.

With this capability, the 6,500 kg (14,300 lb) Webb will look at how the first galaxies formed in the early universe, study star formation, learn more about how galaxies evolve, and focus on exoplanets in other solar systems to seek out evidence of potential life.

Unfortunately, this super vision requires the JWST to operate at temperatures below -223.2 °C (-369.7 °F), which is difficult to achieve in the full glare of the Sun. To do this, the telescope is equipped with a sun shield about the size of a tennis court that is made of five layers of thin sheets of a polyimide film called Kapton that are coated with aluminum. This material is stable across a wide range of temperatures and insulates the telescope, allowing the spacecraft to be hotter than boiling water on one side, but colder than liquid oxygen on the other.

Eoin Treacy's view

The James Webb telescope made headlines over Christmas because it is the most ambitious international space project to be launched in quite some time. It will not be the last. There are at least five more telescopes due for launch in the next decade. That virtually ensures we will “see” alien life before we ever come face to face with aliens. No wonder NASA is consulting with theologians.