Radio Telescope

• 27 Jun 2023

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.

Note:

• 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.

• Examples of Radio Telescopes:
  • Giant Metrewave Radio Telescope (India)
  • SARAS 3 (India)
  • Atacama Large Millimetre/submillimetre Array (ALMA) (Atacama Desert, Chile)
  • Five-hundred-metre Aperture Spherical Telescope (FAST) (China) (one of the biggest with a 500-metre-wide dish.

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