What is the James Webb Space Telescope?

Webb will answer questions about our place in the cosmos.

The James Webb Space Telescope will study every phase of cosmic history — from within our solar system to distant galaxies in the early universe. As an infrared telescope, Webb will explore science questions to help us understand the origins of the universe and our place in it.

Webb is the largest space telescope ever built.

Webb stands at more than three stories tall and is as broad as a tennis court. As the world’s most complex and powerful space science observatory. It will transform our view of the universe. 

18 gold-plated segments make up Webb’s iconic mirror.

The mirror is over six times bigger in area than the Hubble Space Telescope’s.


The mirror segments are covered with a golf ball’s mass of gold, which optimizes them for reflecting infrared light. The coating is so thin that a human hair is 1,000 times thicker!

Webb is neatly folded into a rocket to unfold in space.

The observatory will travel to an orbit about one million miles away from Earth and undergo six months of commissioning in space — unfolding its mirrors, sunshield, and other smaller systems; cooling down; aligning; and calibrating.

It will observe a part of space and time never seen before.

Webb’s infrared capabilities will allow it to gaze into the age when the very first stars and galaxies formed, over 13.5 billion years ago. 

Webb features unprecedented resolution and sensitivity.

It will shed light on how galaxies evolve, how stars and planetary systems are born, and how the building blocks of life could form on other planets, showing us things never before seen by any other telescope.

It can seek the building blocks of life on other worlds.

Webb will observe and conduct studies of planets located in the habitable zones of nearby stars, the regions where a planet could harbor liquid water on its surface.

Webb is a powerful tool for studying the nearby universe.

Scientists will use the space telescope to study planets and other bodies in our solar system to determine their origin and evolution and compare them with exoplanets, planets that orbit other stars.

Take Mars for example. Webb will be able to study the Red Planet’s local features. It will observe whether the atmosphere of Mars reveals any history of habitability, as well as how the atmosphere has changed over time. 

Webb is a massive international effort.

A joint mission between NASA, the European Space Agency, and the Canadian Space Agency, it’s the largest international space science project in U.S. history. Thousands of scientists, engineers, and technicians from 14 countries and 29 U.S. states designed and built Webb.