MeerKAT telescope discovers universe’s ‘unknown unknowns’

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An international team of astronomers has uncovered unusual features in the radio galaxy ESO 137-006 using MeerKAT data.

This is according to the South African Radio Astronomy Observatory (SARAO), a facility of the National Research Foundation, responsible for managing all radio astronomy initiatives and facilities in SA, including the MeerKAT Radio Telescope in the Karoo, and the Geodesy and VLBI activities at the HartRAO facility.

Launched in 2018, the South African MeerKAT radio telescope is a precursor to the Square Kilometre Array (SKA), which aims to answer fundamental astrophysical questions about the nature of objects in the Universe.

The MeerKAT is currently made up of 64 dishes, each 13.5m in diameter. However, it recently received R800 million funding from Germany and SA that will see it get an additional 20 dishes.

The SKA project is being built by an international consortium that includes Canada, China, India, Italy, New Zealand, Spain, Sweden, the Netherlands and the UK, and will be co-hosted in SA and Australia.

It will be built in two main phases, with construction of the first phase planned to start later this year. Some elements will be operational by 2020, with full operation under way in 2025.

SARAO says ESO 137-006 is a fascinating galaxy residing in the Norma cluster of galaxies, and one of the brightest objects in the southern sky at radio wavelengths.

It notes the classical picture of a radio galaxy consists of an active galactic nucleus (AGN, hosting a growing supermassive black hole), shooting out two jets of plasma filled with particles that move at speeds close to the speed of light.

The material within the jets eventually slows down and billows out, forming large radio lobes, says SARAO, adding that ESO 137-006 is characterised by two such lobes of very bright radio emission.

“New features have been uncovered in this galaxy in the form of multiple, extremely collimated threads of radio emission connecting the lobes of the galaxy,” says Mpati Ramatsoku, a research fellow at Rhodes University and lead author of the study.

“The radio emission from the threads is likely synchrotron radiation caused by the high-energy electrons spiralling in a magnetic field.”

However, SARAO points out the nature of these unusual features is unclear. It is possible these features may be unique to ESO 137-006, because of its harsh environment, but it is equally possible that these features are common in radio galaxies but, so far, it has been unable to detect them due to sensitivity and resolution limits, it explains.

According to the team that made this discovery, which is composed of collaborators from SA and Italy and is partly funded by the European Research Council, further observations and theoretical efforts are required to clarify the nature of these newly discovered features.

Ramatsoku points out that understanding the nature and the physics of these collimated synchrotron threads could open a new science case for sensitive radio interferometers like MeerKAT and, in the future, the SKA.

“This is exciting because we did not expect it at all,” says professor Oleg Smirnov, head of the Radio Astronomy Research Group at SARAO. “Such serendipitous discoveries are very important for MeerKAT because it highlights its incredible capacity for finding the ‘unknown unknowns’ in our Universe,” he says.

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