Incredible Indians: Desi astronomers discover largest ‘giant radio galaxies’
Ateam of astronomers from India has reported the discovery of a large number of extremely rare kind of galaxies called ‘giant radio galaxies’ (GRGs), the largest galaxies known in the universe. The last six decades of radio astronomy research has led to the detection of thousands of radio galaxies. However, only about 300 of them can be classified as GRGs. The reasons behind their large size and rarity are unknown.
“The huge size of GRGs has defied any theoretical explanation so far. Our work will help in understanding how these galaxies grow to be so large,” said lead researcher Pratik Dabhade, at Inter-University Centre for Astronomy and Astrophysics (IUCAA, Pune) and also at the Netherlands’ Leiden Observatory.
Dabhade worked with Joydeep Bagchi (IUCAA), Mamta Pommier (CNRS Observatoire de Lyon), Madhuri Gaikwad (NCRA-TIFR Pune and Max-Planck Institute Bonn), Shishir Sankhyayan (IISER Pune) and Somak Raychaudhury (IUCAA).
The team carried out a systematic search for these radio giants and found a large sample of GRGs, using a nearly 20-year-old radio survey. In the journal Monthly Notices of the Royal Astronomical Society, the scientists report the discovery of 25 GRGs from the National Radio Astronomy Observatory Very Large Array Sky Survey.
These extremely active form of galaxies harbour a super massive black hole ‘central-engine’ at the nucleus, which ejects a pair of high energy particle jets nearly at the speed of light, which terminate into two giant radio lobes.
GRGs are visible only to radio telescopes. These behemoths span nearly three million light years across, or even more sometimes. This size corresponds to stacking nearly 33 Milky Way like galaxies in a line.