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Gravitational Lensing

Topics Covered:

  1. Awareness in space.

Gravitational Lensing


What to study?

For Prelims and mains: what is gravitational lensing, why is it useful and Overview of James Webb telescope.


Context: Using NASA’s James Webb Space Telescope as a sort of time machine, researchers plan to investigate how new stars are born, with the help of a natural phenomenon called “gravitational lensing”.


What is gravitational lensing? How it works?

  • Gravitational lensing is an effect of Einstein’s theory of general relativity – simply put, mass bends light.
  • The gravitational field of a massive object will extend far into space, and cause light rays passing close to that object (and thus through its gravitational field) to be bent and refocused somewhere else.
  • The more massive the object, the stronger its gravitational field and hence the greater the bending of light rays – just like using denser materials to make optical lenses results in a greater amount of refraction.


Why is lensing useful? 

  1. Gravitational lensing is useful to cosmologists because it is directly sensitive to the amount and distribution of dark matter.
  2. Lensing can help astronomers work out exactly how much dark matter there is in the Universe as a whole and also how it is distributed.
  3. Lensing has also been used to help verify the existence of dark matter itself.


What is the James Webb Space Telescope?

  1. The James Webb Space Telescope, also called Webb or JWST, is a large, space-based observatory, optimized for infrared wavelengths, which will complement and extend the discoveries of the Hubble Space Telescope.
  2. It will cover longer wavelengths of light than Hubble and will have greatly improved sensitivity.
  3. The longer wavelengths enable JWST to look further back in time to see the first galaxies that formed in the early universe, and to peer inside dust clouds where stars and planetary systems are forming today.


Why is Webb an infrared telescope?

By viewing the universe at infrared wavelengths Webb will show us things never before seen by any other telescope. It is only at infrared wavelengths that we can see the first stars and galaxies forming after the Big Bang. And it is with infrared light that we can see stars and planetary systems forming inside clouds of dust that are opaque to visible light.


Who is James Webb?

This space-based observatory is named after James E. Webb (1906- 1992), NASA’s second administrator. Webb is best known for leading Apollo, a series of lunar exploration programs that landed the first humans on the Moon. However, he also initiated a vigorous space science program that was responsible for more than 75 launches during his tenure, including America’s first interplanetary explorers.


Sources: the Hindu.