Launched on Christmas Day 2021, the James Webb Space Telescope began science operations in mid-2022. What followed has reshaped multiple areas of astrophysics.
Early Universe Galaxies JWST was designed to see the first galaxies forming after the Big Bang. What it found surprised everyone: galaxies that appear too massive, too bright, and too well-formed for the early universe — some at redshifts above z=10, just 300–400 million years after the Big Bang.
These objects challenge galaxy formation models that assumed early structures grew slowly from small seeds. Theorists are now revising simulations and debating whether dark matter dynamics, star formation efficiency, or entirely new physics could explain the observations.
Exoplanet Atmospheres JWST's Near Infrared Spectrograph (NIRSpec) and Mid-Infrared Instrument (MIRI) have analyzed the chemical fingerprints of exoplanet atmospheres in unprecedented detail.
WASP-39b showed carbon dioxide, sulfur dioxide, water, and for the first time, photochemical reactions driven by starlight — essentially weather chemistry on another world.
In 2023, observations of K2-18b showed a tentative signal for dimethyl sulfide — a molecule on Earth produced only by living organisms. The claim remains uncertain and highly debated.
Our Own Solar System JWST has also imaged Jupiter's auroras, tracked storms in unprecedented detail, and mapped Titan's methane lakes. Images of Neptune's rings are the clearest since Voyager 2 flew past in 1989.
The Hubble Tension New JWST Cepheid measurements have sharpened the Hubble Tension — the discrepancy between two ways of measuring the universe's expansion rate. Rather than resolving it, JWST confirms it is real, pointing toward possible new physics beyond the Standard Model of cosmology.
Webb is expected to operate through at least 2041. The first year was only a preview.