What Is the James Webb Space Telescope?

The James Webb Space Telescope rotates so that the user can see all parts of the telescope. The top portion is a mirror made up of shiny golden hexagons and the bottom part is a shiny silver sunshade that looks like a giant foil diamond under the telescope.

An animation illustrating what the James Webb Space Telescope Looks like. Credit: NASA’s Goddard Space Flight Center (modified)

The James Webb Space Telescope is the largest, most powerful space telescope ever built. It will allow scientists to look at what our universe was like about 200 million years after the Big Bang. The telescope will be able to capture images of some of the first galaxies ever formed. It will also be able to observe objects in our solar system from Mars outward, look inside dust clouds to see where new stars and planets are forming and examine the atmospheres of planets orbiting other stars.

Here are some fun facts about the James Webb Space Telescope:

It is very, very big.

The Webb telescope is as tall as a 3-story building and as long as a tennis court! It is so big that it has to fold origami-style to fit inside the rocket to launch. The telescope will unfold, sunshield first, once in space.

An illustration of the James Webb Space Telescope placed next to a 3-story building to show how tall the telescope is. The telescope is also shown sitting above a tennis court to show that the foil-like sunshade is as long as a tennis court.

The James Webb Space Telescope is about the same size as a tennis court and about as tall as a 3-story building! Credit: NASA/JPL-Caltech

It can see through dust clouds.

The same image side-by-side, with the left showing a smokey room and the right showing glowing people via infrared cameras.

Infrared cameras can see through dust and smoke. Credit: NASA/IPAC/Pasadena Fire Dept.

The James Webb Space Telescope sees the universe in light that is invisible to human eyes. This light is called infrared radiation, and we can feel it as heat. Firefighters use infrared cameras to see and rescue people through the smoke in a fire. The James Webb Space Telescope will use its infrared cameras to see through dust in our universe. Stars and planets form inside those dust clouds, so peeking inside could lead to exciting new discoveries! It will also be able to see objects (like the first galaxies) that are so far away that the expansion of the universe has made their light shift from visible to infrared!

It wears a "hat" to help block heat and light from the Sun.

Animation of the Webb telescope sunshielf unfolding.

This animation shows how the sunshield will unfold when the Webb telescope reaches its home in orbit. Credit: NASA

The Webb telescope’s cameras are sensitive to heat from the Sun. Just like you might wear a hat or a visor to block the Sun from your eyes, Webb has a sunshield to protect its instruments and mirrors. The telescope’s sunshield is about the size of a tennis court. The temperature difference between the sun-facing and shaded sides of the telescope is more than 600 degrees Fahrenheit!

It uses giant, gold-coated mirrors to see the universe.

The giant golden mirror of the James Webb Space Telescope made up of smaller golden hexagons. Three engineers in white clean room suits are standing on a platform to examine the mirror.

Engineers inspecting the Webb telescope’s mirrors at NASA’s Goddard Space Flight Center. Credit: NASA/Chris Gunn

Space telescopes “see” by using mirrors to collect and focus light from distant stars. (Check out our telescopes page to learn more about how space telescopes work.) The bigger the mirror, the more details the telescope can see. It’s very difficult to launch a giant, heavy mirror into space. So, engineers gave the Webb telescope 18 smaller mirrors that fit together like a puzzle. The mirrors fold up inside the rocket, then unfold to form one large mirror in orbit.

Why are the mirrors gold? A thin layer of gold helps the mirrors reflect infrared light!

It will be hunting for signs of life on other planets.

Could life survive on this faraway planet? Astronomers study the light from stars and planets to see if they might have the ingredients for life. Animation credit: NASA/ESA/Dani Player (STScI), Music credit: Steve Combs

Our solar system isn’t the only home for planets! Scientists have discovered thousands of planets orbiting stars other than our Sun. These are called exoplanets. The James Webb Space Telescope will help to study the atmospheres of exoplanets. Could the atmospheres of some exoplanets hold the building blocks for life? We will find out soon!

It’s launching soon!

The James Webb Space Telescope is scheduled to launch on December 18, 2021. Want to stay up to date and learn more about NASA’s biggest and most powerful telescope? Find more facts, photos, videos and more at the James Webb Space Telescope Website!

Related resources from NASA

NASA Exoplanets: What is the habitable zone?
James Webb Space Telescope Poster
Lesson Plans, Activities, Resources & Programs For Informal Education
Teachable Moment: Learn About the Universe With the James Webb Space Telescope

article last updated September 30, 2021
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