International Space Agencies – Missions and Discoveries

How James Webb Telescope seeks to unlock Universe’s Secrets


From UPSC perspective, the following things are important :

Prelims level : JWST

Mains level : Not Much

Today, NASA’s James Webb Space Telescope (JWST), the largest and most powerful space telescope ever built, will be launched from French Guiana, on the northeast coast of South America on the European Ariane 5 rocket.

James Webb Space Telescope

  • JWST is a space telescope jointly developed by NASA, the European Space Agency (ESA), and the Canadian Space Agency (CSA).
  • It is planned to succeed the Hubble Space Telescope as NASA’s flagship astrophysics mission.
  • It will conduct a broad range of investigations across the fields of astronomy and cosmology, including:
  1. Observing some of the most distant events and objects in the universe such as the formation of the first galaxies
  2. Detailed atmospheric characterization of potentially habitable exoplanets

How is it different from other telescopes?

  • JWST is much more powerful and has the ability to look in the infrared spectrum, which will allow it to peer through much deeper into the universe, and see through obstructions such as gas clouds.
  • As electromagnetic waves travel for long distances, they lose energy, resulting in an increase in their wavelength.
  • An ultraviolet wave, for example, can slowly move into the visible light spectrum and the infrared spectrum, and further weaken to microwaves or radio waves, as it loses energy.
  • Hubble was designed to look mainly into the ultraviolet and visible regions of the electromagnetic spectrum.
  • JWST is primarily an infrared telescope, the first of its kind.

Special features of JWST

(1) Time machine in space

  • Powerful space telescopes, like JWST or the Hubble Telescope, are often called time machines because of their ability to view very faraway objects.
  • The light coming from those objects, stars or galaxies, which is captured by these telescopes, began its journey millions of years earlier.
  • Essentially, what these telescopes see are images of these stars or galaxies as they were millions of years ago.
  • The more distant the planet or star, the farther back in time are the telescopes able to see.

(2) Farthest from Earth

  • JWST will also be positioned much deeper into space, about a million miles from Earth, at a spot known as L2.
  • It is one of the five points, known as Lagrange’s points, in any revolving two-body system like Earth and Sun, where the gravitational forces of the two large bodies cancel each other out.
  • Objects placed at these positions are relatively stable and require minimal external energy to keep them there. L2 is a position directly behind Earth in the line joining the Sun and the Earth.
  • It would be shielded from the Sun by the Earth as it goes around the Sun, in sync with the Earth.

(3) Engineering marvel

  • JWST has one large mirror, with a diameter of 21 feet (the height of a typical two-storey building), that will capture the infra-red light coming in from the deep universe while facing away from the Sun.
  • It will be shielded by a five-layer, tennis court-sized, kite-shaped sunscreen that is designed to block the heat from Sun and ensure the extremely cool temperatures that the instruments are built to operate at.
  • Temperatures on the sun-facing side can get as high as 110°C, while the other side would be maintained at –200° to –230°C.
  • The extremely cold temperatures are needed to detect the extremely faint heat signals from distant galaxies.
  • The mirror as well as the sunscreen is so large they could not have fit into any rocket. They have been built as foldable items and would be unraveled in space.


UPSC 2022 countdown has begun! Get your personal guidance plan now! (Click here)

Get an IAS/IPS ranker as your 1: 1 personal mentor for UPSC 2024

Attend Now

Notify of
Inline Feedbacks
View all comments


Join us across Social Media platforms.