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 Blazar emission mechanisms


Gamma-ray flux variability of luminous and high energy blazars: clues to blazar emission mechanisms

      WHY IN NEWS:

Hot from PIB !

MINISTRY? :-Ministry of Science & Technology
SYLLABUS COVERED: GS 3:Science and Tech


For PRELIMS it is important to understand the concept of Black Hole and AGN ! This can be asked in Prelims 2020.


Researchers from the Indian Institute of Astrophysics (IIA), Bangalore, an autonomous institute of the Department of Science & Technology, Govt. of India, have conducted the first systematic study on the gamma-ray flux variability nature on different types of blazars.


  • At the center of most galaxies, there’s a massive black hole that can have mass of millions or even billions of Suns that accrete gas, dust, and stellar debris around it.
  • As these material falls towards the black hole, their gravitational energy gets converted to light forming active galactic nuclei (AGN).
  • A minority of AGN (~15%) emit collimated charged particles called jets travelling at speeds close to the speed of light. 


Blazars are AGN whose jets are aligned with the observer’s line of sight.

Blazar - Wikipedia

  • Some blazars are thought to host binary black holes in them and could be potential targets for future gravitational-wave searches.
  • Their study could provide clues to the processes happening close to the black hole, not visible through direct imaging.


  • The results of this work will thus fill the gap on the knowledge of the high energy flux variability nature of blazars.
  • Blazars are the most luminous and energetic objects in the known universe were found to be emitters of gamma-rays in the 1990s.
  • It is only with the capability of Fermi Gamma-ray space telescope (launched in 2008) to scan the entire sky once in three hours.


  • One of the open problems in high energy astrophysics is to localize the site for the production of gamma-rays.
  • Gamma-ray band is one of the bands of the electromagnetic spectrum on which there is limited knowledge on the flux variability of blazars.
  • With the availability of near-simultaneous data covering the gamma-ray, X-ray, ultra-violet, optical, and infrared bands, the existing notion on high energy emission in blazars is challenged.


  • This band needs to be explored as this is the energy range where the high energy emission from blazars peaks.
  • Exploring this band of the electromagnetic spectrum will provide key inputs to constrain the high energy production site as well as the high energy emission processes.
  • The expertise of handling high energy data from celestial sources gained in this work will build capacity to interpret the gamma-ray data that will emerge from India’s upcoming facility, the Major Atmospheric Cerenkov Experiment Telescope as well as from any X-ray missions by India in the future.
Major Atmospheric Cerenkov Experiment Telescope (MACE) is an Imaging Atmospheric Cerenkov telescope (IACT) located at Hanle, Ladakh, India.

      IASbhai WINDUP: 

The results obtained from this particular piece of work will provide key inputs to the problem of finding the high energy gamma-ray production site in blazars.

Variability studies in the high energy gamma-ray band can help one to locate the high energy emission site and the high energy emission process.

Now, we are entering an era of multi-messenger astronomy, where light is not the only information we can collect from the heavens.

  • Gravitational waves first detected in 2015 allow astronomers to observe collisions of black holes and neutron stars.
  • Tracking neutrinos to their source would help astronomers understand the physics behind extreme environments, like the relativistic jets of a blazar, beyond what light alone can tell us.

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