International Space Agencies – Missions and Discoveries

James Webb: The most powerful space telescope


From UPSC perspective, the following things are important :

Prelims level : James Webb Space Telescope

Mains level : Dark Ages of the Univers

On Dec 18, 2021, after years of delays, the James Webb Space Telescope is scheduled to launch into orbit and usher in the next era of astronomy.

James Webb Space Telescope

  • JWST is a joint NASA–ESA–CSA space telescope that is planned to succeed the Hubble Space Telescope as NASA’s flagship astrophysics mission
  • It is the most powerful space telescope ever built.
  • It will enable a broad range of investigations across the fields of astronomy and cosmology, including observing some of the most distant events and objects in the universe,
  • It would help understand events such as the formation of the first galaxies, and detailed atmospheric characterization of potentially habitable exoplanets.

Its significance

  • Some have called JSWT the “telescope that ate astronomy.”
  • It is said to look back in time to the Dark Ages of the universe.

What does the ‘Dark Ages’ of the universe mean?

  • Evidence shows that the universe started with an event called the Big Bang 13.8 billion years ago, which left it in an ultra-hot, ultra-dense state.
  • The universe immediately began expanding and cooling after the Big Bang.
  • One second after the Big Bang, the universe was a hundred trillion miles across with an average temperature of an incredible 18 billion F (10 billion C).
  • Around 400,000 years after the Big Bang, the universe was 10 million light-years across and the temperature had cooled to 5,500 F (3,000 C).
  • Throughout this time, space was filled with a smooth soup of high-energy particles, radiation, hydrogen and helium.
  • There was no structure. As the expanding universe became bigger and colder, the soup thinned out and everything faded to black.

This was the start of what astronomers call the Dark Ages of the universe.

How will JWST study this?

Ans. Looking for the first light

  • The Dark Ages ended when gravity formed the first stars and galaxies that eventually began to emit the first light.
  • Astronomers aim to study this fascinating and important era of the universe, but detecting first light is incredibly challenging.
  • Compared to massive, bright galaxies of today, the first objects were very small and due to the constant expansion of the universe, they’re now tens of billions of light years away from Earth.
  • Also, the earliest stars were surrounded by gas left over from their formation and this gas acted like fog that absorbed most of the light.
  • It took several hundred million years for radiation to blast away the fog. This early light is very faint by the time it gets to Earth.

Try this PYQ:

Consider the following phenomena:

  1. Light is affected by gravity.
  2. The Universe is constantly expanding.
  3. Matter warps its surrounding space-time.

Which of the above is/are the predictions of Albert Einstein’s General Theory of Relativity, often discussed in media?

(a) 1 and 2 only

(b) 3 only

(c) 1 and 3 only

(d) 1, 2 and 3


Post your answers here.
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khyati gupta
khyati gupta
1 year ago
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Deepti Panwar
Deepti Panwar
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