James Webb Space Telescope

The James Webb Space Telescope is the product of an international collaboration between NASA, the European Space Agency (ESA), and the Canadian Space Agency (CSA). Development began in the mid-1990s under the name Next Generation Space Telescope before being renamed in 2002 after James E. Webb, NASA's administrator during the Apollo era.

JWST's primary mirror is a 6.5-metre gold-coated beryllium segmented reflector composed of 18 hexagonal segments. This design allows the mirror to fold for launch and unfold once in space — a complex mechanical deployment that was executed flawlessly following the telescope's launch on Christmas Day 2021.

Operating at the Sun-Earth L2 Lagrange point approximately 1.5 million kilometres from Earth, JWST maintains a stable position that allows it to remain shielded from the Sun, Earth, and Moon by a five-layer sunshield the size of a tennis court. This shield keeps the telescope's instruments at approximately −233 °C (40 K), necessary for detecting faint infrared signals.

JWST carries four primary scientific instruments: the Near-Infrared Camera (NIRCam), the Near-Infrared Spectrograph (NIRSpec), the Mid-Infrared Instrument (MIRI), and the Near-Infrared Imager and Slitless Spectrograph (NIRISS). Each instrument serves a distinct scientific purpose and covers different wavelength ranges.

NIRCam is the telescope's primary imager, sensitive to light in the range of 0.6 to 5 microns. It captures the photons from the earliest galaxies and stars, as well as young stars in the Milky Way and debris disks where planetary systems are forming.

MIRI operates at mid-infrared wavelengths (5 to 28 microns) and is cooled further to approximately 7 K by an active cryocooler. It is capable of imaging distant galaxies, newly forming stars, and comets — and played a key role in characterising exoplanet atmospheres.

Within its first months of operation, JWST detected galaxies forming just 300 million years after the Big Bang — far older than any previously observed. These findings suggest that galaxy formation in the early universe was more rapid and diverse than leading models had predicted.

JWST's spectroscopic observations of the exoplanet WASP-39b revealed the first definitive detection of carbon dioxide in an exoplanet atmosphere. Subsequent observations of other exoplanets have detected water vapour, sulfur dioxide, and complex organic molecules — dramatically expanding our understanding of planetary atmospheric chemistry.

In the Milky Way, JWST has captured extraordinary detail in stellar nurseries such as the Carina Nebula and Pillars of Creation, revealing previously invisible protostars and refining models of star formation. Its observations of the galactic centre have provided new data on the supermassive black hole Sagittarius A*.

The Space Telescope Science Institute (STScI) in Baltimore, Maryland, operates JWST on behalf of NASA. Observing time is allocated through a competitive peer-review process, with proposals submitted annually by astronomers from around the world. Approved programmes span targets from objects in our solar system to the most distant galaxies.

JWST's observations are not conducted in real time by operators — rather, pre-programmed observation sequences are uploaded to the telescope and executed autonomously. Data is transmitted to Earth via the Deep Space Network and made publicly available after a proprietary period during which the principal investigators have exclusive access.

The James Webb Space Telescope represents one of the most significant leaps in observational astronomy since the Hubble Space Telescope. Its ability to peer into the infrared spectrum means it can see through dust clouds that block visible light — revealing the interiors of star-forming regions, the atmospheres of distant planets, and the very first light of the universe.

By observing the universe at redshifts previously inaccessible, JWST is effectively looking back in time to within a few hundred million years of the Big Bang. The data it collects has already prompted revisions to the Lambda CDM model of cosmology and will continue to refine our understanding of dark matter, dark energy, and the large-scale structure of the universe.