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Radio Telescope

  • 27 Jun 2023
  • 4 min read

Why in News?

Telescopes are indispensable tools for astronomers, enabling them to observe and study celestial objects.

  • Among the various types of telescopes, radio telescopes are gaining traction by playing a crucial role in unveiling the mysteries of the universe by detecting radio waves.

What is a Radio Telescope?

  • About:
    • A radio telescope is a device that detects and analyses radio waves from astronomical objects in the sky.
    • Radio waves are a type of electromagnetic radiation that have wavelengths ranging from about 1 millimetre to 10 metres.
      • They can penetrate dust and gas clouds that block visible light, so radio telescopes can reveal hidden structures and phenomena in the universe.
  • Features:
    • They are typically situated on the ground rather than in orbit due to their large size.
    • It consists of two main components: a large antenna and a sensitive receiver.
      • The antenna is usually a parabolic dish that reflects and focuses the incoming radio waves to a focal point.
      • The receiver amplifies and converts the radio signals into electrical signals that can be recorded and analysed by computers.
  • Significance:
    • It can operate day and night, unlike optical telescopes that need clear and dark skies.
    • It can observe objects that are too faint or too distant to be seen by optical telescopes, such as the cosmic microwave background radiation, pulsars, quasars, and black holes.
    • It can study the chemical composition and physical conditions of interstellar gas and dust clouds by detecting the spectral lines of various atoms and molecules.
    • It can measure the magnetic fields and rotation rates of stars and galaxies by detecting the polarisation of radio waves.


  • A pulsar (from pulsating radio source) is a highly magnetised rotating neutron star that emits beams of electromagnetic radiation out of its magnetic poles.
    • Most neutron stars are observed as pulsars.
  • Quasars are very luminous objects in faraway galaxies that emit jets at radio frequencies.
    • Among the brightest objects in the universe, a quasar’s light outshines that of all the stars in its host galaxy combined, and its jets and winds shape the galaxy in which it resides.

UPSC Civil Services Examination, Previous Year Question (PYQ)

Q. Consider the following (2008):

Assertion (A): Radio waves bend in a magnetic field.

Reason (R): Radio waves are electromagnetic in nature.

Which of the following is correct?

(a) Both A and R are individually true, and R is the correct explanation of A

(b) Both A and R are individually true, but R is not the correct explanation of A

(c) A is true but R is false

(d) A is false but R is true

Ans: (a)

Q. A layer in the Earth’s atmosphere called Ionosphere facilitates radio communication. Why? (2011)

  1. The presence of ozone cause the reflection of radio waves to Earth.
  2. Radio waves have a very long wavelength.

Which of the statements given above is/are correct?

(a) 1 only
(b) 2 only
(c) Both 1 and 2 
(d) Neither 1 nor 2

Ans: (d)

Source: TH

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