The James Webb Space Telescope: What It Is and How It Works
Updated November 2, 2026.
The James Webb Space Telescope is an infrared observatory that launched on December 25, 2021. According to Wikipedia, it can detect objects up to 100 times fainter than the ones Hubble can see. Its first full-color images were released on July 11, 2022. It cost just under $10 billion and works far from home.
Where it is
Webb does not orbit Earth the way Hubble does. It sits near the Sun-Earth L2 point, about 930,000 miles (1.5 million km) away, which is almost four times the distance to the Moon. From there, the Sun and Earth stay on one side of the telescope, with the Moon nearby, and that helps keep it cold. It is a remote spot.
It launched on an Ariane 5 rocket from Kourou, in French Guiana. It was a Christmas Day launch. It went well.
The mirror and the instruments
The main mirror is 21 feet (6.5 meters) across. It is made of beryllium, coated in gold and split into 18 hexagonal segments. Together they work as one big mirror. Gold reflects infrared light well. Webb observes wavelengths from 0.6 to 28.5 micrometers, a range that runs from red light our eyes can just see to the mid-infrared. Almost all of it lies beyond human vision.
It carries four main instruments. Each has an alphabet-soup name: NIRCam and NIRSpec, plus MIRI and FGS/NIRISS. Some take pictures, others split light into colors to study what objects are made of, and one helps point the telescope precisely.
Cost and lifetime
The total cost was just under $10 billion. It was a big investment. The mission was planned for 10 years, but the expected lifetime reaches 20, and the limit is the fuel it uses to stay in position.
| Fact | Value |
|---|---|
| Launch | December 25, 2021, on an Ariane 5 |
| First images released | July 11, 2022 |
| Mirror | 21 feet (6.5 m), 18 hexagonal segments |
| Distance from Earth | about 930,000 miles (1.5 million km) |
| Light it observes | 0.6 to 28.5 micrometers |
| Total cost | just under $10 billion |
Frequently asked questions
What is the James Webb Space Telescope?
It is a space telescope that observes infrared light. It launched on December 25, 2021, on an Ariane 5 rocket and works near the Sun-Earth L2 point.
Where is the James Webb Space Telescope?
Near the Sun-Earth L2 point, about 930,000 miles (1.5 million km) from Earth, much farther than the Moon.
How is Webb different from Hubble?
Hubble sees mostly visible and ultraviolet light. Webb sees infrared and can detect objects up to 100 times fainter, according to Wikipedia.
How much did Webb cost?
Just under $10 billion, according to Wikipedia.
How long will Webb last?
The expected lifetime is 20 years, while the original mission was planned for 10, according to the telescope’s Wikipedia page.
Read next: The Hubble Space Telescope: What It Is and What Changed After 1990 and The International Space Station: How It Works and When It Ends.
Sources: James Webb Space Telescope, Wikipedia.
Featured image: NASA/MSFC/David Higginbotham, Public domain, via Wikimedia Commons.
