Lesson · beginner · 5 min
Why Infrared Sees the Early Universe
Learn how cosmic expansion shifts ancient starlight into infrared wavelengths that Webb is built to collect.
Learning goal
After this short lesson you should be able to explain why an infrared telescope is essential for studying the earliest galaxies.
The short story
- Early galaxies emitted a lot of ultraviolet and optical light.
- Expansion of space stretched that light toward longer wavelengths.
- By the time the light reaches us, much of it is infrared.
- Webb's mirrors and instruments are optimized for that infrared window.
Connect it to today's discovery
When you read a Webb headline about an unexpectedly mature early galaxy, ask two questions:
- What redshift (look-back time) is claimed?
- Was the redshift estimated from imaging colors, or confirmed with spectroscopy?
Concepts
Seen in discoveries
- Early Galaxies Challenge Simple Growth Models
- Webb's Star-Filled Portrait of the Pillars of Creation
- Webb's Cosmic Cliffs in the Carina Nebula
- Euclid's View of the Perseus Cluster of Galaxies
- Webb Finds a Dusty Cat's Tail in Beta Pictoris
- Webb's Detailed Portrait of Herbig-Haro 46/47
- Webb's Portrait of Stephan's Quintet
- Webb Captures Wolf-Rayet 124's Winds and Dust
- Webb's Infrared View of Starburst Galaxy M82
- Webb's New Look at the Cartwheel Galaxy
- Webb Peers Through Pandora's Cluster
- Webb's Detailed Beauty of the Ring Nebula
- Webb's Infrared View of Sagittarius C