Northern Cape telescope spots ‘troublesome’ cosmic beast

Staff Reporter|Published 1 month ago

The MeerKAT telescope is located in the Northern Cape, near the small town of Carnarvon. This location in the Karoo was chosen because of its low levels of radio-frequency interference, making it an ideal location for sensitive radio astronomy observations. File picture: South African Radio Astronomy Observatory

SOUTH Africa's MeerKAT radio telescope, located in the Northern Cape, has made an extraordinary discovery - a giant radio galaxy named ‘Inkathazo’, which means "trouble" in the isiXhosa and isiZulu languages.

This groundbreaking find provides new insights into the development of the Universe's largest structures, though it also raises perplexing questions about their origins. The discovery has been detailed in a study published in the Monthly Notices of the Royal Astronomical Society.

A Rare Cosmic Phenomenon

Giant radio galaxies (GRGs) are immense celestial structures that emit jets of hot plasma stretching millions of light-years across intergalactic space. These jets, which glow at radio frequencies, are powered by supermassive black holes situated at the centres of galaxies.

The newly discovered giant radio galaxy ‘Inkathazo’. The glowing plasma jets, as seen by the MeerKAT telescope, are shown in red and yellow. The starlight from other surrounding galaxies can be seen in the background. Picture: KKL Charlton (UCT), MeerKAT, HSC, CARTA, IDIA

Previously considered rare, the discovery rate of GRGs has significantly increased in recent years thanks to advanced radio telescopes like MeerKAT, which is located outside the small Northern Cape town of Carnarvon.

“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 the University of Cape Town and the study's lead author. “Research into GRGs is developing so rapidly that it’s becoming hard to keep up. It’s incredibly exciting!”

Inkathazo: A Unique Giant

The recently unveiled behemoth, Inkathazo, stands out for its extraordinary size and unusual characteristics. Detailed images captured by MeerKAT show plasma jets spanning an incredible 3.3 million light-years - over 32 times the diameter of the Milky Way.

The galaxy's distinctive features make it challenging for researchers to decipher its underlying physics. “We nicknamed this giant galaxy ‘Inkathazo’ … because it has been a bit troublesome to understand the physics behind what’s going on here,” said Charlton

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

Adding to the intrigue, Inkathazo is located at the centre of a galaxy cluster, an environment thought to inhibit the growth of such massive jets.

“This is an exciting and unexpected discovery,” said Dr Kshitij Thorat of the University of Pretoria, a co-author of the study. “Finding a GRG in a cluster environment raises questions about the role of environmental interactions in the formation and evolution of these giant galaxies.”

Probing the Unknown

To investigate further, researchers leveraged MeerKAT's exceptional capabilities to create high-resolution spectral age maps, which analyse the plasma's age across different parts of the galaxy. These maps revealed that some electrons in the jets had been unexpectedly energised, possibly through interactions with hot gas in the galaxy cluster.

A spectral age map of ‘Inkathazo’. Cyan and green show younger plasma, while purple indicates older plasma. Picture: KKL Charlton (UCT), MeerKAT, HSC, CARTA, IDIA

“This discovery has given us a unique opportunity to study GRG physics in extraordinary detail,” Thorat noted. “The findings challenge existing models and suggest that we don’t yet understand much of the complicated plasma physics at play in these extreme galaxies.”

Unlocking the Southern Sky

While most GRGs have been identified in the northern sky using European telescopes, the southern hemisphere remains largely unexplored for these phenomena. The MeerKAT telescope has already discovered three GRGs in a relatively small patch of sky known as COSMOS, an area equivalent to the size of five full moons. Two GRGs were initially documented in 2021, with Inkathazo uncovered during subsequent observations.

“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,” said Dr Jacinta Delhaize, a researcher at the University of Cape Town and lead author of the 2021 publication. “MeerKAT is incredibly powerful and in a perfect location, so is excellently poised to uncover and learn more about them.”

Operated by the South African Radio Astronomy Observatory (SARAO), MeerKAT continues to reveal the secrets of the southern sky. As a precursor to the upcoming Square Kilometre Array (SKA), MeerKAT’s sensitivity and resolution are paving the way for future breakthroughs.

“We’re entering an exciting era of radio astronomy,” 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.”

Source: SARAO