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How does the camera on the James Webb Space Telescope work and see so far out? – Kieran G., age 12, Minnesota
Imagine a camera so powerful it can see light from galaxies that formed more than 13 billion years ago. That’s exactly what NASA’s James Webb Space Telescope is built to do.
Since it launched in December 2021, Webb has been orbiting more than a million miles from Earth, capturing breathtaking images of deep space. But how does it actually work? And how can it see so far? The secret lies in its powerful cameras – especially ones that don’t see light the way our eyes do.
I’m an astrophysicist who studies galaxies and supermassive black holes, and the Webb telescope is an incredible tool for observing some of the earliest galaxies and black holes in the universe.
When Webb takes a picture of a distant galaxy, astronomers like me are actually seeing what that galaxy looked like billions of years ago. The light from that galaxy has been traveling across space for the billions of years it takes to reach the telescope’s mirror. It’s like having a time machine that takes snapshots of the early universe.
By using a giant mirror to collect ancient light, Webb has been discovering new secrets about the universe.
A telescope that sees heat
Unlike regular cameras or even the Hubble Space Telescope, which take images of visible light, Webb is designed to see a kind of light that’s invisible to your eyes: infrared light. Infrared light has longer wavelengths than visible light, which is why our eyes can’t detect it. But with the right instruments, Webb can capture infrared light to study some of the earliest and most distant objects in the universe.
Infrared cameras, like night-vision goggles, allow you to ‘see’ the infrared waves emitting from warm objects such as humans and animals. The temperatures for the images are in degrees Fahrenheit.
NASA/JPL-Caltech
Although the human eye cannot see it, people can detect infrared light as a form of heat using specialized technology, such as infrared cameras or thermal sensors. For example, night-vision goggles use infrared light to detect warm objects in the dark. Webb uses the same idea to study stars, galaxies and planets.
Why infrared? When visible light from faraway galaxies travels across the universe, it stretches out. This is because the universe is expanding. That stretching turns visible light into infrared light. So, the most distant galaxies in space don’t shine in visible light anymore – they glow in faint infrared. That’s the light Webb is built to detect.
