The radio bubbles extend from between the two nearest antennas to the upper right corner. Many magnetised filaments can be seen running parallel to the bubbles. In this composite view, the sky to the left of the second nearest antenna is the night sky visible to the unaided eye, and the radio image to the right has been enlarged to highlight its fine features. Picture: SUPPLIED
The radio bubbles extend from between the two nearest antennas to the upper right corner. Many magnetised filaments can be seen running parallel to the bubbles. In this composite view, the sky to the left of the second nearest antenna is the night sky visible to the unaided eye, and the radio image to the right has been enlarged to highlight its fine features. Picture: SUPPLIED

Scientists are celebrating their first major discovery with SA’s powerful MeerKAT radio telescope, announcing on Wednesday that they have spotted a pair of giant elongated bubbles stretching out of the centre of the Milky Way.

The bubbles were probably formed in a violent eruption near the galaxy’s supermassive black hole between three and six-million years ago and shed new light on the origin of mysterious radio filaments that have puzzled astronomers for the past 35 years.

The discovery is an important affirmation that MeerKAT is capable of science beyond the reach of older radio telescopes such as the Very Large Array (VLA) in New Mexico, said Ferndano Camilo, chief scientist at the South African Radio Astronomy Observatory (SARAO) and co-author of a paper describing the discovery published in the scientific journal, Nature.

MeerKAT, which was officially inaugurated by President Cyril Ramaphosa in 2018, is the most sensitive radio telescope in the southern hemisphere. Its 64 dishes are located in a remote site near Carnarvon in the sparsely populated Northern Cape, and will be incorporated into the international Square Kilometre Array (SKA), which will be the world’s largest telescope when completed.  Construction of phase 1 of the SKA is expected to begin late in 2020, and aims to add another 133 dishes to MeerKAT along with 130,000 smaller radio antennas in Australia.

Last year’s inauguration saw scientists unveil the first image taken with all 64 dishes of the MeerKAT, a striking view of the central region of the Milky Way intended to show off the telescope’s technical capabilities. That image now turns out to be more than just a pretty picture, said Camilo.

“In the process of analysing the data, purely by chance, we saw these bubbles coming out to the north and south of the centre of our galaxy,” said Camilo.

“Some of these features were known already, but no-one had detected anything in the southern half and no-one had realised that they might form part of a coherent whole formed by one event,” he said. The boundaries of the bubbles emit radio waves, which can easily penetrate the thick clouds of dust blocking visible light from the centre of the galaxy.

The bubbles tower hundreds of light years above and below the centre of the Milky Way, about 25,000 light years away from our solar system. A light year is the distance light travels in a year — 9.46-trillion kilometres.

The centre of the Milky Way is relatively calm compared to other galaxies which have much more active black holes at their centre, but can periodically flare up as it devours huge clumps of dust and gas, said the paper’s lead author Ian Heywood, of the University of Oxford.

“It’s possible that one such feeding frenzy triggered powerful outbursts that inflated this previously unseen feature,” he said.

The region about the Milky Way’s central black hole is very different to the rest of the galaxy’s environment and contains very long, narrow radio filaments not seen anywhere else. These filaments were discovered in the 1980s, and have until now remained a mystery. It turns out that most of the filaments lie within the bubbles, suggesting they were created by the same explosive event, said Camilo.

MeerKAT was optimised to meet the needs of 10 large survey projects that were approved in 2010. These projects get two-thirds of its observing time over the next five years, and the rest is to be allocated to smaller proposals.

“The fact that the very first scientific result is on something that the MeerKAT was not fundamentally designed to do suggests that in years to come we will find many more things that were not planned,” said Camilo.

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