South African team uncovers 'Inkathazo': a distinctive giant radio galaxy

In a remarkable stride forward for astrophysics, researchers from the University of Cape Town (UCT) and the powerful MeerKAT radio telescope have unveiled the existence of a rare giant radio galaxy named Inkathazo. This discovery, published on Monday, January 20, 2025, in the Monthly Notices of the Royal Astronomical Society, not only sheds light on these vast cosmic structures but also poses intriguing challenges for astronomers as they work to comprehend their unique characteristics.

Giant radio galaxies (GRGs) represent some of the most expansive structures in the universe. These colossal entities are made up of massive galaxies that emit plasma jets stretching millions of light-years through intergalactic space, all powered by supermassive black holes at their cores. Although once deemed rare, an explosion of GRG discoveries has occurred in the past five years, thanks to groundbreaking advancements in radio astronomy—a trend captured by the capabilities of the MeerKAT telescope.

“The number of GRG discoveries has absolutely exploded in the past five years thanks to powerful new telescopes like MeerKAT,” said Kathleen Charlton, a Master’s student at UCT and the first author of the study. “Research into GRGs is developing so rapidly that it’s becoming hard to keep up. It’s incredibly exciting!”

What sets Inkathazo apart from its peers is its strikingly unusual plasma jets that extend a staggering 3.3 million light-years—more than 32 times the size of the Milky Way. The name Inkathazo, which translates to “trouble” in isiZulu and isiXhosa, aptly reflects the complexities and peculiarities of this galaxy, which have posed significant challenges for researchers attempting to grasp its enigmatic physics.

“It doesn’t have the same characteristics as many other giant radio galaxies,” Charlton commented. “For example, the plasma jets have an unusual shape. Rather than extending straight across from end to end, one of the jets is bent.”

Utilising the advanced technology of MeerKAT, researchers crafted high-resolution spectral age maps of Inkathazo. These maps enabled them to track the age of the plasma jets across varying regions, unveiling unexpected energy spikes in the electrons within the jets. This intriguing finding is likely attributed to collisions with hot gas located between galaxies in the cluster, challenging existing models of plasma physics and further emphasising the intricacies of these cosmic giants.

Dr Jacinta Delhaize, a researcher at UCT and a part of the team behind the 2021 publication, stressed the significance of MeerKAT in uncovering these celestial wonders. “The fact that we unveiled three GRGs by pointing MeerKAT at a single patch of sky goes to show that there is likely a huge treasure trove of undiscovered GRGs in the southern sky,” she remarked.

As the operational groundwork for the forthcoming Square Kilometre Array (SKA), MeerKAT has established itself as a pioneering instrument for astronomers delving into the uncharted territories of the southern sky. “We’re entering an exciting era of radio astronomy,” Dr Delhaize added. “While MeerKAT has taken us further than ever before, the SKA will allow us to push these boundaries even further and hopefully solve some of the mysteries surrounding enigmatic objects like giant radio galaxies.”

This groundbreaking discovery of Inkathazo reinforces the pivotal role of South Africa and the University of Cape Town in advancing humanity's grasp of the universe, highlighting the significance of cutting-edge research and international collaboration in decoding the mysteries of our cosmos.