South Africa’s MeerKAT Telescope Discovers New Giant Radio Galaxy

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The newly discovered giant radio galaxy ‘Inkathazo’. Source: K.K.L Charlton (UCT), MeerKAT, HSC, CARTA, IDIA.

South Africa’s MeerKAT telescope has discovered a new giant radio galaxy, nicknamed ‘Inkathazo,’ meaning ‘trouble’ in Xhosa and Zulu languages, due to the difficulty in understanding the physics behind this discovery. The cosmic megastructure measures 3.3 million light-years, which is 32 times the size of our Milky Way galaxy and is 1.44 billion light-years away from Earth. Researchers anticipate that this discovery, published in the  Monthly Notices of the Royal Astronomical Society, will provide valuable insights into the origins and evolution of some of the universe’s largest structures. 

Giant radio galaxies (GRGs) are massive cosmic structures that shoot out jets of hot plasma, stretching millions of light-years into space. These glowing jets, visible at radio frequencies, are powered by supermassive black holes at the centres of galaxies. GRGs were once considered rare, but advanced radio telescopes like South Africa’s MeerKAT have dramatically changed this view by uncovering many more of these massive galaxies.

“The number of GRG discoveries has 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 first author of the new study. She added, “We nicknamed this giant galaxy ‘Inkathazo,’ meaning ‘trouble’, because understanding the physics behind what’s going on here has been a bit troublesome.” Kathleen further noted that ‘Inkathazo’, whose catalogue name is MGTC J100022.85+031520.4, has different characteristics compared to other giant radio galaxies. For example, one of the plasma jets has an unusual shape, bending instead of extending straight from end to end.

The newly discovered GRG also lives at the very heart of a cluster of galaxies rather than in relative isolation, which should make it difficult for the plasma jets to grow to such enormous sizes.”This is an exciting and unexpected discovery,” said Dr Kshitij Thorat, a co-author of the study from the University of Pretoria. Finding a GRG in a cluster environment raises questions about the role of environmental interactions in the formation and evolution of these giant galaxies.

Leveraging MeerKAT’s Advanced Capabilities

To learn more about this cosmic mystery, the researchers used MeerKAT’s advanced technology and high sensitivity to produce some of the most detailed spectral age maps ever created for GRGs. These maps measure the age of the plasma in different parts of the GRG, offering insights into the physical processes at play. The findings uncovered fascinating complexities in Inkathazo’s jets, with some electrons unexpectedly gaining extra energy. The team suspects this might happen when the jets interact with hot gas in the spaces between galaxies within the cluster.

The newly discovered giant radio galaxy ‘Inkathazo’. Source: K.K.L Charlton (UCT), MeerKAT, HSC, CARTA, IDIA.

Most GRGs have been discovered in the northern hemisphere using European telescopes, leaving the southern sky largely unexplored for such massive structures. However, Inkathazo is not an isolated case. Astronomers identified it as the third GRG in a small region of the sky, about the size of five full moons, known as “COSMOS.” In 2021, an international group of astronomers, part of the “MIGHTEE” collaboration, used the MeerKAT telescope to study COSMOS. They quickly identified the other two GRGs and published their findings during their observations.

“The discovery of three GRGs by focusing MeerKAT on just one small area of the sky suggests that there is likely a vast number of undiscovered GRGs in the southern sky,” said Dr Jacinta Delhaize, a researcher at the University of Cape Town and lead author of the published paper. MeerKAT is an exceptionally powerful telescope in an ideal location, making it ideally suited to uncover and study these giant structures.

An Exciting Era for African Radio Astronomy

MeerKAT will soon become part of the Square Kilometre Array (SKA), a USD 2.2 billion project comprising interconnected radio telescope networks across Africa and Australia. This includes 197 radio dishes in the Karoo region of South Africa’s Northern Cape and several other antennas across eight SKA partner countries that will support the network. Together with another 131,072 antennas in Western Australia, these instruments will create a combined collecting area of one square kilometre across two continents, enabling the detection of extremely faint radio signals. These discoveries come as the African continent intensifies its effort to advance its radio astronomy capabilities through capacity building and infrastructure development.