James Webb Captured Galaxies Forming Just 300 Million Years After the Big Bang

The James Webb Space Telescope, launched in December 2021, was designed to look further back in time than any instrument in human history. It has succeeded — and the images have stunned the astronomical community.

JWST's deep-field images have captured galaxies whose light left them when the universe was only 300 million years old — about 2% of its current age. These galaxies are not just baby smudges; they are surprisingly well-formed, far more massive and structured than theory predicted should exist so early.

Why This Is Shocking

Pre-JWST, models of galaxy formation suggested that fully-grown galaxies the size of the Milky Way should not exist until at least 1 billion years after the Big Bang. JWST has found candidates that look fully developed at 500 million years, raising fundamental questions about how galaxies form and how dark matter clumps in the early universe.

The Telescope Itself

• Mirror: 6.5 meters across — the largest space telescope ever launched
• Sun shield: 5 layers, the size of a tennis court
• Operating temperature: -223°C, achieved by passive cooling alone
• Distance from Earth: 1.5 million km, at the L2 Lagrange point
• Sensitivity: Can detect a candle flame at the distance of the Moon