A team of international astronomers has used the Giant Metrewave Radio Telescope (GMRT) National Centre for Radio Astrophysics (NCRA) to discover the biggest pair of plasma jets ever seen to emanate from a supermassive black hole, spanning a size of 23 million light-years end to end. The size of the jets is more than a 100 times the size of the Milky Way.
Martijn Oei, a post-doctoral scholar at the California Institute of Technology (Caltech) and the lead author of a new Nature paper reporting these findings, said, “This pair is not just the size of a solar system, or a galaxy; we are talking about 140 Milky Way diameters!”
The jet megastructure has been nicknamed ‘Porphyrion’ after a giant in Greek mythology and dates back to a time when our universe was 6.3 billion years’ old. These powerful outflows—with a total power output equivalent to trillions of Suns—shoot out from either side of a supermassive black hole at the heart of a remote galaxy.
Oei said, “At the centre of every major galaxy, there is a big black hole of about a million to a billion solar masses. It swallows stars, dust and plasma, basically everything that comes close, but a small fraction of the material that comes close to the black hole is ejected outward in the form of such jets.”
The gigantic jet system is one of thousands of faint megastructures originally found using Europe’s LOFAR (Low-Frequency Array) radio telescope.
Martin Hardcastle, second author of the study and a professor of astrophysics at the University of Hertfordshire in England, said, “The existence of these giants was known before we started the campaign, but we had no idea that there would turn out to be so many.”
To determine the length of the jets, a powerful radio telescope was needed that could trace the jets back to the galaxy from which they emerged. This is where the GMRT came into the picture. Oei’s team used sensitive, high-resolution GMRT observations to identify the host galaxy that spawned the jets. Once the host was identified using the GMRT, the researchers then used the Keck I optical telescope in Hawaii to obtain the distance. ‘Porphyrion’ is 7.5 billion light-years from the Earth, which means it existed when our universe was less than half its present age of 13.8 billion years. Without the precise position provided by the GMRT observations, it would have been impossible to identify the optical host galaxy and determine the giant extent of the radio megastructure.
Having a greater reach also implies that the jumbo jets could have a wider influence on nearby galaxies. Co-author of the study, George Djorgovski, professor of astronomy and data science at Caltech, said, “We believe that galaxies and their central supermassive black holes co-evolve, and one key aspect of this is that they put out huge amounts of energy in the form of jets that can affect the growth of their host galaxies and other galaxies near them. This discovery shows that their effects can extend much further out than we thought.”
As a next step, Oei wants to better understand how these megastructures influence their surroundings. Oei is specifically interested in finding out the extent to which these giant jets spread magnetism. Oei said, “The magnetism on our planet allows life to thrive, so we want to understand how it came to be. We know magnetism starts in the cosmic web, then makes its way into galaxies and stars, and eventually to planets, but where does it start? Have these giant jets spread magnetism through the cosmos?”
The study of supermassive black hole jets in radio galaxies has been an area of research where the GMRT has made several important contributions over the last two decades. The discovery of ‘Porphyrion’ is another achievement for the GMRT in this active area of research in astrophysics.
