Page 44 - University of Pretoria RESEARCH REVIEW 2018

Bringing the invisible into focus
Roger Deane, Department of Physics
At the heart of every galaxy lies a supermassive black hole
with a mass ranging from around a million to over a billion times that of the sun. This is true of the largest galaxies
in the universe to more medium-sized examples such
as the Milky Way which has over 10 billion stars. These objects are regions of space so dense that not even light can escape their gravitational pull, resulting in Nature self- cloaking, using the laws of physics.
that he had something to offer – to build highly realistic simulations of the Earth-sized telescope.
It was in this area – testing the capabilities and limits of this Earth- sized telescope – that Roger Deane and research groups at UP and Rhodes University developed a world- first simulation of the global network of antennas and the atmosphere above. Their work was focused on understanding the performance of this Earth-sized telescope, and to generate confidence in the calibration and imaging results that the EHT released in 2019.
Even in the absence of adverse weather effects and imperfect engineering, the technique that the EHT uses, aperture synthesis, is a complex process. Its inventor, Sir Martin Ryle, was awarded the Nobel
Studying and understanding black holes is the primary motivation of the global Event Horizon Telescope (EHT) collaboration: how matter is accreted onto black holes, how black holes accelerate particles along jets at velocities near that of light and, most ambitiously, to test whether Einstein was right about the fundamental force of gravity.
Capturing an image of the extremes of nature required that the EHT assemble a telescope that used the extremities
of the Earth. This is exactly what the EHT did: individual antennas had to be at planet-scale distances apart, and on top of mountains and volcanoes, to try to peek above the atmosphere, specifically above the water vapour that can so easily remove any signature of a black hole shadow.
Roger Deane, Associate Professor
in the Department of Physics, understood as far back as 2012 when the EHT was still a loose grouping
of scientists, that he wanted in, and
On 10 April 2019, the Event Horizon Telescope Collaboration made science history by revealing the first image of a black hole to the world, a ring of fire that one could say marks an exit point from our universe. It was a historic achievement for science: the first direct visual confirmation of the existence of these gravitational behemoths predicted by Einstein’s general theory of relativity a century earlier.
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