Where is the James Webb Space Telescope now?

The James Webb Space Telescope is a telescope in space, built by NASA with the European and Canadian space agencies. It collects infrared light, too red for our eyes to see, from some of the faintest and farthest things in the sky.

Webb works about 1.6 million kilometres from Earth. The Moon, at about 380,000 kilometres, is much closer: Webb is about 4.1 times as far away.

Webb does not orbit Earth, as the Hubble Space Telescope does. It orbits the Sun, and a balance of the Sun's and Earth's pull keeps it in step with us. It circles the Sun at about 30.06 kilometres per second. Since you opened this page, Webb has travelled 0 kilometres around the Sun. The point it loops around is called L2, on the far side of Earth from the Sun.

From there the Sun, Earth and Moon are always on the same side. So a single shield can keep their light and heat away from the telescope. It also never passes into Earth's shadow, and can watch the sky day and night.

Webb left Europe's Spaceport in French Guiana on 25 December 2021, on an Ariane 5 rocket. It took about a month to reach its orbit around L2.

Its main mirror is 6.5 metres across, too wide to launch in one piece. So it is built from 18 hexagonal segments of beryllium, a strong, light metal. Each carries a thin coat of gold, which reflects infrared light well. The mirror folded for launch, like the leaves of a drop-leaf table, and opened in space.

The launch was so precise that Webb saved much of its fuel for later. NASA expects that fuel to last well beyond the science mission it was planned for.

Webb sees mostly infrared light, the kind we feel as warmth. A warm telescope would glow in that light itself, and the faint glow of distant galaxies would be lost.

So Webb hides behind a sunshield roughly the size of a tennis court. It has 5 layers of thin plastic film, each thinner than a human hair, coated with metal. Each layer is cooler than the one before. The side facing the Sun is hot. Behind the shield, the telescope stays below 50 kelvin.

One instrument, MIRI, needs its detectors colder still. It carries its own cooler to get there.

On 12 July 2022 NASA showed the first full-colour images from Webb. The telescope is a partnership with the European and Canadian space agencies.

One image was a deep field towards a cluster of galaxies called SMACS 0723. The patch of sky it covers is about the size of a grain of sand held at arm's length. Yet it is full of galaxies. Webb gathered it in less than a day.

The cluster's gravity bends and magnifies the light of galaxies far behind it, like a lens. With its help, Webb picked out some of the most distant galaxies detected at the time.

The Earth formed about 4.5 billion years ago. By then the light from MoM-z14 had already been on its way for billions of years. It set out before the Sun, the Earth or anything on it existed.

While it travelled, the Sun and the Earth formed, and life appeared on our planet. All that time the light kept coming.

That old light ends its journey on a gold mirror we designed, folded and sent away. We are made of the same universe it set out from. Now, for the first time, we can watch its first galaxies taking shape.