James Webb Space Telescope launch
On Christmas morning a $10-billion origami telescope left for L2 — and cleared all 344 single points of failure.
The moment of James Webb Space Telescope launch: https://nowsky.org/e/jwst-launch — opens at the right place and time, replayable, no login.
Available views: Orbit ✓ · Sky — (not visible in the sky)
The story
On the morning of 25 December 2021 the James Webb Space Telescope left French Guiana on an Ariane 5. Twenty-five years of development, ten billion dollars, and a destination 1.5 million km away where nothing could be repaired — it was the most nerve-racking Christmas present in the history of astronomy.
The following month was one deployment after another: a five-layer sunshield the size of a tennis court, eighteen gold-plated beryllium mirror segments — 344 single points of failure, and the control room breathed again as each one passed. The last wing of the primary mirror unfolded on 8 January, and the telescope reached its orbit at the Sun–Earth L2 point on 24 January.
Ariane 5's precise launch saved so much correction fuel that the expected lifetime doubled from ten years to twenty. Since the first deep field was released on 12 July 2022, Webb has been bringing the universe's first galaxies into view — JADES-GS-z14-0, seen 300 million years after the Big Bang, is the record so far.
"Hubble's successor" is only half right. Working at different wavelengths (infrared), it sees a different universe, which is why the two telescopes still work together. Requests for observing time exceed supply more than five to one every year. The orbit view replays the month-long cruise to L2.
Why it matters
Webb sees in infrared the light of the first galaxies, stretched by cosmic expansion. It has found dozens of galaxies from before 500 million years after the Big Bang, beyond Hubble's reach, and their unexpected size and brightness forced a rewrite of early star-formation models.
Exoplanet atmospheric spectroscopy is its second pillar. In 2022 it made the first clear detection of carbon dioxide at WASP-39b, and it is reading the atmospheres of K2-18b and the TRAPPIST-1 planets one by one. The search for biosignatures on Earth-like worlds extends from this technique.
Passing all 344 single points of failure was a milestone of space engineering. Unfolding a telescope where no repair is possible became the premise for Roman (2027) and for the design of the Habitable Worlds Observatory of the 2040s.
How to watch
Webb sits in a halo orbit around the Sun–Earth L2 point, 1.5 million km from Earth — a 17th-magnitude speck barely reachable by large amateur telescopes. Zoom in on Earth in the orbit view and Webb's marker is drawn at L2.
The orbit replay draws the cruise from the launch on 25 December 2021 to arrival at L2 a month later; following Earth shows Webb receding on the side away from the Sun and orbiting the Sun in step with Earth.
Webb's targets can be found at their real distances in the sky view's deep-sky list and the 3-D interstellar view — the Carina Nebula (7,500 light-years), the Southern Ring Nebula, Stephan's Quintet, and JADES-GS-z14-0 at 13.4 billion light-years.
See this for yourself — replay the moment in the orbit view
Background
Planned for a 2007 launch at 500 million dollars, the project slipped fourteen years and grew twenty-fold in cost through technical difficulty and management problems. Congress considered cancelling it in 2011; it survived, and a sunshield tear during testing in 2018 cost another year.
The mirror is 6.5 m across, seven times Hubble's area, and is cooled to −233 °C behind the sunshield for infrared work; the mid-infrared instrument MIRI has its own cooler taking it to −266 °C.
In May 2022 a micrometeoroid struck one mirror segment and left minor damage with no effect on performance. More than twenty years of fuel remain, and observations are expected to continue into the 2030s.
Webb is named for James Webb, the NASA administrator who led the Apollo programme in the 1960s; calls to rename it before the 2021 launch were declined by NASA. It launched from French Guiana because ESA provided the rocket in exchange for a share of observing time under an international partnership, while the Canadian Space Agency supplied the fine guidance sensor and a spectrograph. The three-agency division of labour was broader than Hubble’s (NASA and ESA) and became the model for Roman and the Habitable Worlds Observatory.
FAQ
Why go to L2?
The Sun, Earth and Moon all lie on one side there, so the sunshield can block them and cool the telescope to −233 °C.
Does it replace Hubble?
No — Webb works in infrared and Hubble in visible and ultraviolet light; they observe together.
How long will it last?
Thanks to the precise launch, more than twenty years of fuel remain and observations should run into the 2030s.
What is the most distant galaxy it has seen?
JADES-GS-z14-0, seen about 300 million years after the Big Bang, 13.4 billion light-years away.
Related
- Hubble Space Telescope launch
- Roman Space Telescope launch
- Roman's first big surveys
- James Webb — object index
- Hubble Space Telescope — object index
Times and figures are approximate — verify with official sources when planning travel. Simulation uses J2000 mean elements.