The James Webb Space Telescope: Five Years of Discoveries That Rewrote Astronomy

Since first light in mid-2022, the James Webb Space Telescope has done something rare in astronomy: it has surprised the experts. Galaxies appeared earlier and brighter than models predicted. Atmospheres were mapped on planets we did not know existed a decade ago. The deepest pinpricks of the sky filled with structure no human had ever seen.

Galaxies at the edge of time

JWST has discovered galaxies whose light left them when the universe was less than 300 million years old — and they are larger and more mature than theorists thought possible. The galaxy JADES-GS-z14-0 is the current record holder, observed at a redshift of 14.32, just 290 million years after the Big Bang.

Five discoveries that changed our picture

1. Galaxies in the first 300 million years that already host massive stars and possibly black holes.
2. CO₂ and methane detected in exoplanet atmospheres, including K2-18 b — a hint of a possible water-rich world.
3. Direct imaging of exoplanets in the mid-infrared, including Saturn-mass companions to nearby stars.
4. Detailed maps of carbon-rich dust in protoplanetary disks where planets are forming today.
5. New views of solar system worlds — Neptune's rings sharper than Voyager 2 captured them, and methane fluorescence on Mars in real time.

Primary mirror

6.5 m, gold-coated beryllium, 18 hexagonal segments

Sunshield

5 layers of Kapton, 21 m × 14 m, blocks the Sun by 1 million times

Operating temperature

-233 °C (40 K)

Location

Sun-Earth L2 Lagrange point, 1.5 million km away

Launch

December 25, 2021 on Ariane 5

Cost

~$10 billion

How JWST is different from Hubble

Hubble works mostly in visible light from low Earth orbit. JWST works in infrared from a much colder, more distant location — the L2 Lagrange point. Infrared lets it see through dust, observe cooler objects, and look at galaxies whose light has been redshifted by cosmic expansion. Webb sees what Hubble cannot.

How long will JWST last?

The mission was designed for 5 years and budgeted for 10. Thanks to a precise Ariane 5 launch that used very little of Webb's onboard fuel, NASA estimates the spacecraft can operate for at least 20 years before propellant for station-keeping runs out.