SouthAfrica.info (Johannesburg)

South African Scientist Leads Triple Black Hole Discovery

Cape Town astronomer Roger Deane and a team of South African-funded researchers have discovered a trio of closely orbiting supermassive black holes in a galaxy more than 4-billion light years away - confirmation of the country's fast-growing expertise in the field of radio astronomy.

The discovery of the triple black hole system, the tightest trio of black holes known to date, "is remarkable since most galaxies have just one at their centre" and suggests that closely packed supermassive black holes are far more common than previously thought, Square Kilometre Array (SKA) South Africa said in a statement on Friday.

SKA South Africa funded the research leading to the discovery, which has been published in the scientific journal Nature.

"Four South African institutions - the Universities of Cape Town and the Western Cape, as well as Rhodes University and SKA South Africa - are represented by the research team, which is a very positive confirmation of the dynamic and significant radio astronomy which has developed rapidly in South Africa," SKA SA project director Bernie Fanaroff said in a statement on Monday.

"The discovery demonstrates that South Africa has the scientific and technical expertise to be a world leader in radio astronomy and to contribute directly to gravitational wave experiments that will provide fundamental insights not only to astronomy, but also more broadly to physics."

According to SKA South Africa, multiple supermassive black hole systems are thought to have a significant impact on the way galaxies evolve, particularly through their impact on stars and gas as they spiral in towards one another.

When these black holes get very close to one another they are expected to emit gravitational waves. Einstein predicted these ripples in space-time a century ago, and the giant Square Kilometre Array and MeerKAT radio telescopes being built in South Africa have been designed in part to detect them.

The research team used a technique called Very Long Baseline Interferometry (VLBI) to discover the inner two black holes of the triple system. This technique combines the signals from large radio antennas separated by up to 10 000 kilometres to see detail 50 times finer than that possible with the Hubble Space Telescope.

The discovery was made with the European VLBI Network, an array of European, Chinese, Russian and South African antennas, as well as the 305-metre Arecibo Observatory in Puerto Rico.

"Although they were predicted theoretically, these exotic back hole systems have remained elusive for decades," Fanaroff said. "This discovery suggests that they are more common than previous observations have shown and predicts that the radio telescopes we are building here in South Africa and Africa will be able to discover many more.

"This highlights the high-impact science that will be done with the African VLBI Network, the planned radio telescope comprised of an array of converted telecommunication dishes. It also connects the type of science done with VLBI arrays with the experiments to be performed with MeerKAT and eventually with the SKA."

Research team leader Deane said it was extraordinary that the trio of black holes, "which are at the very extreme of Einstein's theory of general relativity, are orbiting one another at 300 times the speed of sound on Earth.

"Not only that, but using the combined signals from radio telescopes on four continents we were able to observe this exotic system one-third of the way across the Universe. It gives me great excitement, as this is just scratching the surface of a long list of discoveries that will be made possible with the Square Kilometre Array."

The SKA project is an international effort to build mega radio telescope about 100 times more sensitive than the biggest existing radio telescope. The first phase of the SKA will be co-hosted by South Africa and Australia, with eight southern African countries partnering with South Africa during the second phase. Construction is expected to begin in 2017 and conclude in 2024, at an estimated cost to the 10 SKA member countries of €1.5-billion.

South Africa, meanwhile, has begun erecting the 64 antennas that will make up the MeerKAT radio telescope, the country's precursor to the SKA, at the SKA South Africa site outside Carnarvon in the Northern Cape.

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