Indian radio astronomers have announced the discovery of 34 new giant radio sources using data from the TIFR GMRT Sky Survey Alternative Data Release 1 at 150 MHz. Notably, several of these newly identified sources challenge existing theories about their environments, with two in particular pushing the boundaries of current understanding. The unprecedented size and rarity of these giant radio sources continue to intrigue scientists, who are eager to unravel the factors contributing to their massive scale.
The discovery was significantly aided by the Giant Metrewave Radio Telescope (GMRT), situated near Khodad village, approximately 90 km north of Pune, India. Operated by the National Centre for Radio Astrophysics (NCRA) of the Tata Institute of Fundamental Research (TIFR), the GMRT surveyed the radio sky at 150 MHz from 2010 to 2012, covering roughly 90% of the sky. The crucial data from this survey, known as the TIFR GMRT Sky Survey (TGSS), played a key role in the researchers' findings.
The discovery was made by a team including Ph.D. students Netai Bhukta from SKBU and Souvik Manik from MCC, along with astronomers Sabyasachi Pal from MCC and Sushanta K. Mondal from SKBU. Their study utilized low-frequency TGSS data and the high sensitivity of the GMRT, enabling them to identify 34 giant radio sources.
According to a report of NDTV, Giant radio sources are likely to be the largest single structures in the universe, with end-to-end extents of millions of light years. They are driven by supermassive black holes with masses ten million to a billion times that of the Sun, residing at the centre of the host galaxy.
These black holes ionize surrounding matter, creating strong electromagnetic forces that drive material to the edges and generate jets of hot plasma and vast lobes of radio emission. Giant radio sources (GRSs) are thought to represent the final stage in the evolution of radio galaxies. Their immense size provides valuable insights into the development of radio sources and the intergalactic medium. However, detecting GRSs is challenging due to the bridge emission, which often remains obscured between the two lobes. Low-frequency radio surveys, such as TGSS, are more effective for identifying these structures compared to high-frequency surveys.