The James Webb Space Telescope (JWST) is the largest telescope ever placed in space, an infrared observatory operated by NASA in partnership with the European Space Agency and the Canadian Space Agency. It launched on an Ariane 5 rocket from Kourou, French Guiana, on December 25, 2021, and observes from a halo orbit around the Sun-Earth L2 point, about 1.5 million kilometers beyond Earth.[1][2]
Webb was built as the scientific successor to the Hubble Space Telescope. Its 6.5-meter segmented mirror and infrared instruments let it detect galaxies from the universe's first few hundred million years, measure the chemistry of exoplanet atmospheres, and peer through dust clouds that block visible light. Demand from astronomers has broken records every year; its fifth observing cycle began on July 1, 2026.[5]
Development and launch
The project began in 1996 as the Next Generation Space Telescope and survived redesigns, schedule slips, and a near-cancellation by Congress in 2011 before launch. NASA's development and early-operations cost is about 10 billion dollars, with ESA contributing the launch and instrument hardware and Canada the guidance sensor.[2]
The observatory launched folded inside its payload fairing and completed hundreds of deployment steps in its first two weeks, unfurling the sunshield and latching the mirror wings into place. The Ariane 5 flew so accurately that the telescope kept far more station-keeping propellant than planned, enough for more than 20 years of operations.[2] Webb reached L2 on January 24, 2022, and NASA released its first science images, including the SMACS 0723 deep field, on July 11 and 12, 2022.[2]
Observatory design
The primary mirror combines 18 hexagonal beryllium segments, each adjustable to fractions of a wavelength, into a 6.5-meter surface with about six times Hubble's collecting area. A five-layer sunshield the size of a tennis court keeps the telescope side below 50 kelvins so that its own heat does not swamp faint infrared signals; the mid-infrared instrument is chilled further, to about 7 kelvins, by a cryocooler.[1][2] The observatory has absorbed occasional micrometeoroid strikes, including one in May 2022 that left a measurable but small distortion in one mirror segment.[2]
| Instrument | Wavelength range | Contributed by | Role |
|---|---|---|---|
| NIRCam | 0.6-5 microns | University of Arizona | Primary near-infrared camera and coronagraph |
| NIRSpec | 0.6-5.3 microns | ESA | Spectrograph observing up to about 100 objects at once |
| MIRI | 5-28 microns | ESA consortium and NASA JPL | Mid-infrared imaging and spectroscopy |
| FGS/NIRISS | 0.8-5 microns | Canadian Space Agency | Fine guidance and slitless spectroscopy |
The early universe
Webb's deep surveys have pushed the galaxy distance record far beyond Hubble's reach. Spectroscopically confirmed galaxies now include JADES-GS-z14-0, seen about 290 million years after the Big Bang, and MoM-z14, confirmed in 2025 at a slightly greater redshift of about 14.4.[2] Early galaxies proved more numerous and more luminous than most models predicted.
The telescope also revealed a puzzling population of compact, faint crimson objects nicknamed "little red dots." Analyses published in January 2026 argue that many are not ordinary galaxies but "black hole stars": growing supermassive black holes wrapped in dense envelopes of gas, a proposed missing link in how the first black holes gained mass.[6] Webb has likewise confirmed actively feeding supermassive black holes within the universe's first 600 million years, adding pressure on models of early black hole growth.[8]
Exoplanets
In 2022 Webb made the first clear detection of carbon dioxide in an exoplanet atmosphere, at the hot gas giant WASP-39 b.[2] Its transit spectroscopy has since probed the TRAPPIST-1 system's rocky worlds; observations reported in 2025 showed that TRAPPIST-1 d, despite sitting near the habitable zone, lacks an Earth-like atmosphere.[1]
Direct imaging has produced results of its own. In 2025 Webb captured evidence of a Saturn-mass planet orbiting the young star TWA 7, its first direct-image planet discovery, and measured a carbon-rich, potentially moon-forming disk around the planetary-mass companion CT Cha b.[8] In May 2026 astronomers reported that the giant planet WASP-94A b cycles daily between cloudy mornings and clear evenings, with clouds made of rock-forming minerals that condense and evaporate each day.[7]
Solar system and interstellar visitors
Within the solar system, Webb has tracked storms on the giant planets and, working with the Keck II telescope, provided the first evidence of convective methane clouds in the northern hemisphere of Saturn's moon Titan.[1]
Its most watched target of 2025-2026 was 3I/ATLAS, the third known interstellar object, discovered on July 1, 2025. Webb's NIRSpec observations that August, taken while the comet was still 3.32 astronomical units from the Sun, revealed a coma dominated by carbon dioxide, with a CO2-to-water ratio of about 7.6, among the highest ever measured in any comet.[3] Follow-up observations after the comet rounded the Sun in late 2025 measured chemical and isotopic ratios unlike those of solar system comets, and NASA reported that the data point to formation around another star billions of years before the Sun existed.[4]
Operations status
The observatory and all four instruments remained fully operational in mid-2026, nearly four years into a mission with propellant reserves projected to last two decades.[1][2] Interest from researchers keeps climbing: the Cycle 5 call for proposals drew 2,930 submissions, a record for any observatory, from which reviewers selected 254 General Observer programs totaling about 8,000 hours of telescope time. Cycle 5 observations began on July 1, 2026.[5]
References
- James Webb Space Telescope - NASA.
- James Webb Space Telescope - Wikipedia.
- JWST detection of a carbon dioxide dominated gas coma surrounding interstellar object 3I/ATLAS - arXiv.
- NASA's Webb Finds Clues to Ancient, Distant Origin of Comet 3I/ATLAS - NASA.
- JWST Cycle 5 Proposal Selection - Space Telescope Science Institute.
- Those strange red dots in James Webb images finally have an explanation - ScienceDaily.
- NASA's Webb telescope discovers a planet where rock clouds vanish every night - ScienceDaily.
- Press Releases 2025 - ESA/Webb.
