01
International observatory
LUME MISSION RECORD · 05
WEBB · AN INFRARED VIEW OF THE UNIVERSE
The James Webb Space Telescope observes infrared light to study galaxies, stars and planets. Built by NASA, ESA and CSA, it unfolded in space before beginning its observations. Explore how it works and what its images reveal.
LAUNCH25 DEC 2021
OPERATING REGIONSUN–EARTH L2
PRIMARY MIRROR18 SEGMENTS · 6.5 M
THE SAME REGION · DIFFERENT WAVELENGTHS
What infrared light reveals
Some infrared wavelengths pass through dust more easily than visible light. Webb can reveal stars forming inside clouds that hide them from our eyes.
NASA, ESA, CSA, STScI; J. DePasquale, A. Koekemoer, A. Pagan (STScI). ↗
Look at the stars. In Webb’s view of the Pillars of Creation, more stars appear among and around the dusty columns. Both telescopes show the same star-forming region, using different wavelengths.
Look at the colours. Webb’s detectors record infrared light that our eyes cannot see. Colours are assigned to the wavelength ranges to make their differences visible.
NASA · ESA · CSA
The people who built Webb
Scientists, engineers, technicians and support teams worked across countries and organisations. Their tasks included making the mirrors, assembling the instruments, writing software and testing the observatory for launch and operation in space.
- Nearly 20,000
- people involved across the programme’s stages, according to NASA
- 14 countries
- contributed to the international observatory
- 40 million hours
- estimated construction effort, according to ESA/Webb
- 2004–2021
- from the start of construction to launch, following earlier studies and design work
Years of assembly and testing
The mirror segments had to work together as one mirror. The instruments were tested in extreme cold, and the assembled telescope underwent vibration and vacuum tests. Engineers also rehearsed the movements needed to unfold it in space.
Construction began in 2004. Webb launched on 25 December 2021, then spent roughly six months cooling down, aligning its mirrors and checking its instruments before its first science results were released.
Meet the international team · NASASources: NASA programme participation · ESA/Webb construction estimates
THREE FIRST RELEASES · THREE WAYS TO READ LIGHT
Three observations
to explore
Explore a deep field, a star-forming region and measurements of an exoplanet’s atmosphere.
01 · NIRCAMWebb’s First Deep Field
02 · NIRCAMThe Cosmic Cliffs
03 · NIRISSWASP-96 b, measured in transitOfficial Webb imagery · NASA, ESA, CSA and STScI. Full credits, context and source records accompany each observation below.
ENGINEERING BEFORE IMAGERY
How Webb
unfolded in space
Deployment was not a single event. Each completed operation made the next possible, while the observatory travelled away from Earth.
25 December 2021 · Separation
Copyright: ESA/Arianespace; Camera: Réaltra Space Systems Engineering; Music: “Lonely Waltz” by Charlotte Hatherley, used with permission. Original video and credit ↗
A camera on Ariane 5’s upper stage recorded Webb separating from the rocket, with Earth in the background. Its solar panel begins to open 69 seconds after separation, providing power for the journey ahead.
The deployment sequence · Animation
Animation: NASA’s Goddard Space Flight Center. Original video and credit ↗
Webb’s mirror and sunshield were folded to fit inside Ariane 5. This computer animation shows how the spacecraft opened them after launch, with the sequence compressed into a shorter viewing time.
Explore the launch and deployment timeline
02
Built to fold
A full observatory inside a launch vehicle
In its deployed configuration Webb measures roughly 21 × 14 × 8 metres. Its mirror, sunshield and structures had to fold for launch aboard Ariane 5.03
25 Dec 2021 · Launch
The sequence begins
Ariane 5 carried Webb from Europe’s Spaceport in French Guiana. Separation placed the spacecraft on its outward trajectory.04
The first two weeks · Deployment
From spacecraft to observatory
Arrays, antenna, sunshield layers, secondary mirror and primary-mirror wings unfolded through a carefully ordered series of operations.05
24 Jan 2022 · L2
Reaching its observing orbit
Webb entered its operating orbit around the Sun–Earth L2 region, about 1.5 million kilometres from Earth. It circles the Sun while looping around L2; it does not remain fixed at one point.06
Six months · Commissioning
Cold, aligned, calibrated
The observatory cooled, its 18 primary-mirror segments were aligned, and four science instruments were calibrated before routine observations began.07
11–12 Jul 2022 · First science
The first public field
SMACS 0723 was unveiled first, followed by the complete set of Webb’s initial images and spectra.INFRARED · SPECTROSCOPY · EVIDENCE
What we learn
from light
Images show where objects and structures are. Spectra show how their light changes across wavelengths, helping astronomers study what they are made of and how they behave.
Filtered light
Detectors measure infrared light through selected wavelength ranges. Colour is assigned so those measurements can be read by human eyes.
Separating wavelengths
Spectrographs separate light by wavelength. The resulting pattern helps astronomers identify gases and study how an object moves.
Understanding the measurements
Astronomers compare the measurements with physical models to estimate properties such as composition and temperature. The conclusions include uncertainties.
CURATED RECORD
FIRST PUBLIC RELEASE · JULY 2022
Galaxies, stars
and a planet’s atmosphere
Three observations from Webb’s first public release, with explanations of what each reveals.
01 Official release02 Scientific context03 Visible credit
01
Webb’s First Deep Field
Galaxy cluster SMACS 0723 appears as it was 4.6 billion years ago. Its gravity bends and magnifies light from galaxies behind it. Look for the stretched arcs: they are distorted views of more distant galaxies.
- TARGET
- SMACS 0723 · GALAXY CLUSTER
- INSTRUMENT
- NIRCAM · NEAR-INFRARED
- EXPOSURE
- 12.5 HOURS · MULTIPLE WAVELENGTHS
- FIELD
- A GRAIN OF SAND HELD AT ARM’S LENGTH
02
The Cosmic Cliffs
This apparent ridge is the wall of a giant gaseous cavity within NGC 3324. Ultraviolet radiation and stellar winds from massive young stars above the field are eroding the wall, while infrared vision reveals stars and outflows hidden behind dust.
- TARGET
- NGC 3324 · CARINA NEBULA
- INSTRUMENT
- NIRCAM · NEAR-INFRARED
- DISTANCE
- APPROX. 7,600 LIGHT-YEARS
- SCALE
- TALLEST PEAKS · APPROX. 7 LIGHT-YEARS
03
WASP-96 b, measured in transit
As WASP-96 b crossed its star, some starlight passed through the planet’s atmosphere. Different gases absorb different wavelengths. Webb measured these small changes in the light, detecting water vapour and evidence of clouds and possible haze.
- TARGET
- WASP-96 b · HOT GAS GIANT
- METHOD
- TRANSIT · TRANSMISSION SPECTROSCOPY
- INSTRUMENT
- NIRISS · SOSS MODE
- OBSERVATION
- 6.4 HOURS · 0.6–2.8 MICRONS
MEASURED
141 wavelength points showing how much starlight was blocked.
INFERRED
Water vapour, with evidence of clouds and possible haze.
ILLUSTRATED
The planet and star in the background. Webb did not image them directly.
PRIMARY RECORDS
Official sources
GET TO KNOW THE MISSION
Curious about the James Webb Space Telescope?
What is the James Webb Space Telescope?
Webb is a space observatory developed by NASA, ESA and CSA. It studies infrared light from distant galaxies, forming stars, planets and objects in our own Solar System.
Why observe infrared light?
Infrared reveals cool objects and can pass through some dust that blocks visible light. It also lets Webb detect light from distant galaxies stretched to longer wavelengths as the universe expands.
Where is Webb?
It orbits the Sun near the Sun–Earth L2 point, about 1.5 million kilometres from Earth. Its sunshield helps keep the telescope cold enough to detect faint infrared signals.
Are Webb’s images ordinary photographs?
They are built from measurements through selected filters. Infrared wavelengths are assigned visible colours so we can see structures and compare what the different filters reveal.
Read the official explanations: NASA Webb overview ↗ · ESA/Webb questions ↗ · ESA/Webb image processing ↗