James Webb Space Telescope

The James Webb Space Telescope is a space-based observatory designed chiefly to investigate infrared light. Its science program spans the history of the universe, including early galaxies, the formation and evolution of stars and planetary systems, and objects within the Solar System. Infrared observations can reveal comparatively cool objects and light from distant cosmic sources that has been shifted to longer wavelengths as the universe expands. Webb complements other observatories rather than replacing them: its infrared coverage and observing environment provide capabilities distinct from telescopes optimized for other wavelengths.

Webb's 6.6-metre primary mirror consists of 18 hexagonal, gold-coated beryllium segments. The segmented design allowed the mirror to be folded for launch and deployed in space. A large sunshield separates the observatory's warm, sun-facing spacecraft from the cold telescope and instruments, helping limit infrared interference from heat. Webb's four principal scientific instruments are NIRCam, a near-infrared camera; NIRSpec, a near-infrared spectrograph; MIRI, the Mid-Infrared Instrument; and NIRISS, a near-infrared imager and slitless spectrograph. They collect images and spectra in different modes to address questions about astronomical objects and their physical properties.

Webb operates in a halo orbit around the Sun–Earth second Lagrange point, commonly called L2, roughly 1.5 million kilometres from Earth in the direction away from the Sun. This location allows the telescope to keep Earth and the Sun on the same side of its sunshield while maintaining a stable view of the sky. Webb is not in low Earth orbit like the Hubble Space Telescope; it travels around the Sun near L2. It was launched aboard an Ariane 5 rocket on 25 December 2021, reached its L2 orbit in January 2022, and began science operations in July 2022 after deployment and commissioning.

Webb is a partnership among NASA, ESA and the Canadian Space Agency. NASA leads the mission and contributed the observatory and several instruments; ESA contributed the Ariane 5 launch service and the NIRSpec instrument, while Canadian contributions include NIRISS and the Fine Guidance Sensor. The Space Telescope Science Institute in Baltimore operates the observatory and supports the international astronomy community. The mission was built to serve researchers worldwide through a competitive process for scientific observing proposals.

Webb provides observations used to examine galaxies, stars, planetary systems and atmospheres of exoplanets across a broad infrared range. Images show the distribution and structure of sources, while spectra break light into wavelengths that can reveal information about composition, temperature and motion. Scientific findings depend on analysis of particular observations and continue to be refined as data are studied; a telescope image alone does not establish every interpretation proposed for it. Webb's capabilities extend the long-term use of space observatories for astronomy and enable investigations that were difficult or impossible with earlier instruments.