P172+18 Quasar – UPSC Prelims

  • P172+18 is a quasar. It emitted wavelengths with a redshift of 6.8. The higher the redshift of the radio wavelength, the farther away is the source.
  • Redshift is an increase in the wavelength and corresponding decrease in the frequency and photon energy of electromagnetic radiation(such as light).
  • The quasar is also one of the fastest accreting quasars. It means it is accumulating objects from the galaxy at an enormous speed.
  • Further, 90% of the quasars do not emit strong radio waves, making this newly-discovered quasar special.
About Quasars:
  • What are Quasars? Quasars are very luminous objects around black holes in faraway galaxies that emit jets at radio frequencies.
  • Origin of Name: The word quasar is short for “quasi-stellar radio source”. This name, which means star-like emitters of radio waves was given in the 1960s when quasars were first detected.
  • However, now most astronomers know most quasars are faint radio emitters. In addition to radio waves and visible light, quasars also emit ultraviolet rays, infrared waves, X-rays, and gamma-rays.
  • Where are they found? Quasars are only found in galaxies that have supermassive black holes which power these bright discs.
  • How are Quasars formed? Most active galaxies have a supermassive black hole at the centre which sucks in surrounding objects. These objects while moving around a black hole emit energy before being sucked into the black hole. Quasars are formed from this energy.
Key Characteristics of Quasars:
  • Most quasars are larger than our solar system as they are approximately 1 kiloParsec in width. (Parsec is a unit of length used to measure the astronomical objects outside the Solar System. They are approximately equal to 3.26 light-years).
  • Even though quasars are very bright, we cannot see any quasars in the night sky without using a telescope. This is due to their great distance from Earth.
  • Energy from quasars takes billions of years to reach the Earth’s atmosphere. For this reason, the study of quasars can provide astronomers with information about the early stages of the universe.
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