A team of astronomers working at the National Centre for Radio Astrophysics (NCRA, TIFR), Pune have discovered, using the Giant Metrewave Radio Telescope (GMRT), an extremely rare galaxy of gigantic size. This galaxy — located about 9 billion light years away towards the constellation Cetus — emits powerful radio waves and has an end to end extent of a whopping 4 million light years! Such galaxies with extremely large ‘radio size’ are appropriately called giant radio galaxies.
How do galaxies with an optical size of a hundred thousand light years produce radio emission several million light years in extent? It is argued that the presence of a super massive black hole at the centre of the galaxy drives large scale jets of hot plasma in diametrically opposite directions which eventually give rise to large radio lobes (see the image). While radio galaxies with size less than a million light years are common, giant radio galaxies are extremely rare, even more so, at large cosmic distances where only a handful have been discovered so far. This newly discovered galaxy known by its scientific name ‘J021659-044920’ is the newest member of this elite group.