James Webb Space Telescope launch
On Christmas morning 2021 the folded-up James Webb Space Telescope left for L2, 1.5 million km away, and came through every step of an unfolding with no room for error.
Available views: Orbit ✓ · Sky — (not visible in the sky)
The story
On the morning of 25 December 2021 the James Webb Space Telescope lifted off from French Guiana in South America on an Ariane 5 rocket. It had taken about 25 years and roughly 10 billion dollars to build. Its destination was about 1.5 million km from Earth, around four times the distance to the Moon. No one could go there to fix a problem, so the people watching the launch were very tense.
The telescope had been folded up like origami to fit inside the rocket, so over the month after launch it had to be opened one piece at a time. A five-layer sunshield the size of a tennis court was spread out, and eighteen gold-coated, six-sided mirror segments were moved into place. The process included 344 steps where a single failure could endanger the whole mission. The last wing of the mirror unfolded on 8 January 2022, and on 24 January the telescope arrived in its orbit around the Sun–Earth L2 point.
The Ariane 5 sent the telescope off in such a precise direction that much of the fuel meant for course corrections was saved. As a result, the telescope is expected to work for about twenty years, far longer than the original ten-year goal. Since its first science images were released in July 2022, Webb has been finding one early galaxy after another. The galaxy MoM-z14, confirmed in 2025, is seen as it was about 280 million years after the Big Bang.
Webb is often called “Hubble’s successor”, but that is only half true. Hubble mainly sees visible and ultraviolet light, while Webb sees infrared light, which human eyes cannot see. Because they see different kinds of light, they reveal different sides of the universe, and the two telescopes still work together. The orbit view replays Webb’s month-long journey from Earth to the L2 point.
Mission goals
Because the universe keeps expanding, light from very distant galaxies gets stretched during its long journey and becomes infrared. So seeing the oldest galaxies requires an infrared telescope. Webb has found many galaxies from less than 500 million years after the Big Bang, which Hubble could not see. These galaxies turned out bigger and brighter than expected, so scientists are rethinking how quickly stars formed in the early universe.
Studying the air of planets around other stars, called exoplanets, is another major job for Webb. When a planet passes in front of its star, some starlight shines through the planet’s atmosphere, and splitting that light into its colours shows which gases are there. In 2022 Webb made the first clear detection of carbon dioxide on the planet WASP-39b, and it is also studying K2-18b and the planets of TRAPPIST-1.
Successfully unfolding a folded telescope in space was also a milestone in space engineering. Larger space telescopes being planned for the future, such as NASA’s Habitable Worlds Observatory, meant to look for Earth-like planets, are being designed with Webb’s experience in mind. A telescope bigger than a rocket can hold has to be folded and then opened in space.
Mission chronology and background
The project began with a goal of launching in 2007 on a budget of about 500 million dollars. But the technology was extremely difficult and there were management problems too, so the launch slipped by fourteen years and the cost grew about twentyfold. In 2011 members of the US Congress even discussed cancelling it. In 2018 the sunshield tore during testing, delaying the schedule again.
The main mirror is 6.5 m across, giving it nearly six times Hubble’s light-collecting area (Hubble’s mirror is 2.4 m). Infrared light also comes from heat, so a warm telescope would blind itself with its own glow. That is why Webb is chilled behind its sunshield to about −233 °C, and its mid-infrared instrument, MIRI, uses its own cooler to reach −266 °C. In May 2022 a tiny space rock struck one mirror segment, but the telescope still performs better than its targets.
The telescope is named after James Webb, who led NASA in the 1960s and guided the Apollo programme. Webb was built through international cooperation. The European Space Agency supplied the Ariane 5 rocket and parts of the instruments in exchange for a share of observing time, and the Canadian Space Agency provided a sensor that keeps the telescope precisely pointed, along with a science instrument.
Where to see it — sky and simulator
Webb travels in a wide orbit around the Sun–Earth L2 point, about 1.5 million km from Earth. L2 lies on the far side of Earth from the Sun, so the telescope circles the Sun in step with Earth. Zoom in on Earth in the orbit view to see Webb’s marker at L2, and play the replay to follow its path from the launch on 25 December 2021 to its arrival a month later.
Objects Webb has observed can be found at their real distances in the sky view’s deep-sky list and the 3-D interstellar view. They include the Carina Nebula, about 7,600 light-years away, the Southern Ring Nebula, and Stephan’s Quintet, a group of galaxies about 290 million light-years away. Changing the scale in the interstellar view shows just how huge the gap is between a nearby nebula and a distant galaxy.
See this for yourself — replay the moment in the orbit view
FAQ
Why did it go to L2?
From there the Sun, Earth and Moon all lie on one side, so a single sunshield can block their light and heat and keep the telescope at about −233 °C.
Does it replace Hubble?
No. Webb mainly sees infrared light and Hubble visible and ultraviolet light, and the two still observe together.
How long will it last?
Because the launch was so precise and saved fuel, it is expected to last about twenty years, longer than the original ten-year goal.
What is the most distant galaxy it has seen?
A leading example is MoM-z14, confirmed in 2025, seen as it was about 280 million years after the Big Bang.
Related
- Hubble Space Telescope launch
- Roman Space Telescope launch
- Roman's first big surveys
- James Webb — object index
Times and figures are approximate — verify with official sources when planning travel. Simulation uses J2000 mean elements.