What JWST found
Astronomers using the James Webb Space Telescope's NIRSpec spectrograph have spectroscopically confirmed a galaxy at a redshift greater than z = 13 — placing it at a lookback time of roughly 13 billion years, seen when the universe was only about 300 million years old. This is the most distant spectroscopically confirmed galaxy to date. Its existence is already challenging some models of how quickly the first galaxies assembled their mass.
The discovery builds on JWST's First Deep Field, released in July 2022, and the JADES (JWST Advanced Deep Extragalactic Survey) programme. Full details are published in the Webb Telescope news releases.
Why redshift matters
As the universe expands, light travelling through it gets stretched to longer wavelengths — a process called cosmological redshift. The further away a galaxy is, the longer its light has been travelling, and the more it has been redshifted. At z = 13, visible light emitted by stars in the early galaxy has been stretched into the near-infrared — exactly where JWST's detectors are optimised. Hubble, which was optimised for visible light, could not detect these galaxies at all. Our Big Bang guide explains the expanding universe and how we measure it.
What it means for cosmology
The galaxy appears more massive and more structured than standard Lambda-CDM (cold dark matter) models predicted would exist so early. This is not evidence against the Big Bang — the broad picture remains rock solid — but it suggests either galaxy assembly was faster than models assumed, or that processes like early star formation were more efficient. The data is driving a healthy revision of the detailed timeline. ESA's cosmology pages give the broader context. See also our guide on dark matter and dark energy.