International Space Agencies – Missions and Discoveries

James Webb telescope : The most powerful space telescope


From UPSC perspective, the following things are important :

Prelims level: JSWT

Mains level: JSWT, Big bang

James Webb telescopeContext

  • Much of the universe remains unknown. The James Webb telescope will hopefully provide a powerful window to help resolve some of the cosmos’s many mysteries.

What is James Webb Space Telescope (JWST)?

  • It is a space telescope being jointly developed by NASA, the European Space Agency (ESA), and the Canadian Space Agency (CSA).
  • It has taken 30 years and $10bn to develop, and is being described as one of the grand scientific endeavors of the 21st Century.

Where it is placed?

  • The James Webb Space Telescope will not be in orbit around the Earth, like the Hubble Space Telescope is – it will actually orbit the Sun, 1.5 million kilometres (1 million miles) away from the Earth at what is called the second Lagrange point or L2.


  • It will be “a giant leap forward in quest to understand the Universe and our origins”, as it will examine every phase of cosmic history: from the Big Bang to the formation of galaxies, stars, and planets to the evolution of our own Solar System.

james webb telescope Special features of JWST

  • 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.
  • Farthest from Earth: James Webb telescope 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.
  • 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.

What is the goal of this telescope?

  • The telescope will be able to see just about anything in the sky.
  • However, it has one overriding objective – to see the light coming from the very first stars to shine in the Universe.
  • These pioneer stars are thought to have switched on about 100-200 million years after the Big Bang, or a little over 13.5 billion years ago.
  • James Webb telescope will be picking out groupings of these stars.

james webb telescope Its significance

  • It is widely expected to unveil many secrets of the universe, particularly those related to the Formation of stars and galaxies in the early period the first few hundred million years after the Big Bang.
  • Some have called James Webb telescope  the “telescope that ate astronomy”.
  • It is said to look back in time to the Dark Ages of the universe.


  • The universe is vast and most of it is unknown. We hope that the James Webb telescope, over its lifetime would provide us with a powerful window to help resolve some of the many mysteries of the cosmos and make it a little bit more comprehensible.

Mains question

Q. What is James Webb telescope experiment? Do you think it shades light on dark matter? Explain.  

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