Discovery of 34 New Giant Radio Sources

Indian astronomers use the Giant Metrewave Radio Telescope (GMRT) to discover 34 new giant radio sources (GRSs).

Historical Background

• Past Discovery Rate: Only about 100 giant radio sources were known 20 years ago.
• Reason for Limited Discovery: This number was a tiny fraction of the actual population due to observational limitations.
• Advancements in Detection: The commissioning of new telescopes operating at low frequencies, such as GMRT (Giant Metrewave Radio Telescope) and LOFAR (Low-Frequency Array), has significantly increased the number of known giant radio sources to a few thousand.

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Key Points

• Discovery of Giant Radio Sources: A team of Indian radio astronomers has identified 34 new giant radio sources (GRSs). 
  • The findings have been published in the Astrophysical Journal Supplement Series (ApJS) of the American Astronomical Society.
• Challenging Conventional Views: Two of the newly discovered GRSs, J0843+0513 and J1138+4540, challenge the conventional notion that GRSs grow only in low-density environments. 
  • Researchers said that factors other than environmental density play a significant role in the exceptionally large size of Giant Radio Galaxies (GRGs).
• Telescope Used: The discovery was made using the Giant Metrewave Radio Telescope (GMRT), located near Khodad village, about 90 km north of Pune.
  • The GMRT is operated by the National Centre for Radio Astrophysics (NCRA) of the Tata Institute of Fundamental Research (TIFR).
  • This telescope surveyed the radio sky at a low frequency, making it ideal for detecting these faint, distant objects.
• Survey Used: From 2010 to 2012, a survey was performed using the GMRT to map the radio sky at 150 MHz, known as the TIFR GMRT Sky Survey (TGSS) covering about 90% of the sky. 
  • The team of astronomers used TIFR GMRT Sky Survey (TGSS) for their research due to its low frequencies and the sensitivity of the GMRT. 
• Advantages of Low-Frequency Radio Surveys
  • Suitability for Identification: Low-frequency radio surveys are more effective for identifying GRSs compared to higher-frequency surveys.
  • Brightness of Aged Plasma: Aged plasma in GRSs is brighter at low frequencies, making it easier to detect.

Giant Radio Sources (GRS)

• About: Giant Radio Sources (GRS) are among the largest structures in the universe.
  • They are powered by supermassive black holes at their centres, which are millions to billions of times heavier than the Sun.
  • These black holes emit powerful jets of hot plasma that create massive radio-emitting lobes, extending well beyond the visible parts of the galaxy.
• Significance: 
  • Final Stage of Radio Galaxies: GRSs are believed to represent the final stage in the life of a radio galaxy due to their immense size.
  • Insights into Radio Galaxy Evolution: The size and structure of GRSs provide valuable insights into the evolution of radio galaxies.
    • The study of GRSs helps scientists understand the relationship between black hole activity and the evolution of radio galaxies.
  • Understanding Interstitial Space: GRSs offer insights into the interstitial space between the lobes of radio galaxies.
  • Cosmic Matter Distribution and Behavior: Research on giant radio galaxies aids in comprehending the distribution and behaviour of matter in the cosmos.
• Challenges in Observing and Discovering Giant Radio Sources: 
  • Separation Issue: As radio sources grow in size, their ends become more widely separated.
  • Connection Difficulty: The increased separation makes it challenging to observationally connect the ends as part of the same source.

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