Caption: Artist’s impression of gas from a Caption: The galaxy PKS 2014-55 with jets of companion star accreting onto a compact object. plasma extending from the central supermassive Credit: David A. Hardy / astroart.org black hole outwards into an enormous X shape.

of the spectral lines we determine important analytic models, we will continue to choreograph our parameters such as the orbital periods; the dance with the stars, improving our understanding of geometries of the orbits; and the masses of the stars. the Universe and our place in it. The latter is particularly important in distinguishing Cross-hairs between neutron star and black hole accretors. on a Black Hole Shadow with African Telescopes e also use data at radio, infrared, UV, X-ray and gamma-ray wavelengths About the Authors By Roger Deane and Kshitij Thorat W to obtain a complete picture of Dr Itumeleng Monageng received his PhD from the the processes taking place. Analytic and 3D University of Cape Town (UCT) in 2018. He currently Shedding light in the darkest places supercomputer models are used to test our holds a joint position between the South African understanding of the systems and give us clues to Astronomical Observatory and UCT where he conducts ne of the most pressing research One way this is done in astrophysics is to seek out the formation, evolution and final fate of the binaries. research that focuses on the study of X-ray binary stars themes in contemporary exotic cosmic objects that signify some strange using multiwavelength facilities, including SALT and astrophysics is the nature of black event, class, or anomaly which can, in turn, be MeerKAT. South Africa is well-placed to conduct holes; how they form relativistic jets; used as a laboratory in its own right. By seeking multiwavelength studies of binary stars, with leading Assoc. Prof Shazrene Mohamed is an astrophysicist and their relationship to the gas and out strange and special cases of the emission researchers in this field making use of flagship at the SAAO and UCT. Her research focuses on Ostars in their host galaxies. As in many disciplines, associated with black holes, we can (metaphorically) facilities such as SALT and more recently the supercomputer models of stars and their interactions from medical science to psychology, we push to the shed light on these intrinsically dark objects. MeerKAT radio telescope, as well as future facilities with nearby companions. She received her A.B. from extremes to better understand where our theories Harvard and PhD from Oxford. She is an NRF P-rated such as the Vera Rubin Observatory. Through these break down in order to gain new ground and Over the past 18 months, several South African- researcher and UCT VC 2030 Future Leader.

observations, together with our simulations and SAAO improve our models of nature. based researchers were part of two high-visibility >>

20 October 2020 | Science Matters Science Matters | October 2020 21 haystack by surveying large swaths of sky at great depth. In contrast, Earth-sized telescopes such as the EHT and the eventual African VLBI Network are able to make detailed studies of those needles.

n the pursuit of studying exotic radio morphologies, great effort is being put into I developing new antennae in new sites, including Africa, to improve the imaging quality of black Caption: The image of a black hole as captured by the holes and their “shadows”. MeerKAT is also being Event Horizon Telescope enhanced with an extra 20 antennae to become MeerKAT+; and then with a further 113 antennae to become the first phase in the Square Kilometre the edges of a galaxy on scales of millions of light- Array’s mid-frequency component. years. Despite the enormous successes, the MeerKAT he telescopes that generated these two and EHT telescopes are in many ways just getting iconic images, MeerKAT and the Event started. The EHT’s near-term goals include the T Horizon Telescope, are very different challenge of turning ‘mere imagery’ into black-hole Caption: The positions of the telescopes which comprise the Event Horizon Telescope. instruments with very different goals. However, both movies, as well as making precision measurements telescopes rely on a Nobel-prize-winning technique of the size and shape of the black hole at the centre results that revealed extraordinary radio images. called radio interferometry, which is able to stitch of our own galaxy. While not directly related to one another, they serve On the opposite end of the scale to the EHT’s together multiple antenna data streams so that they as informative and exciting examples of exotic radio “zoomed-in” black hole image, the second example, can act as a single virtual telescope tuning into the The ring-like and X-shaped images profiled here are morphologies that can teach us about black holes announced in May of 2020, is a majestic new image symphonies of the universe. just visually enchanting examples of what will be a and their environments. of the entire galaxy PKS 2014-55. PKS 2014-55 is rich tapestry of important scientific advances made an astronomical object which emits radiation in radio In the case of MeerKAT, there are 64 antennae within by these cutting-edge telescopes built entirely or The first example was enabled by the Event Horizon waves. This image was taken by MeerKAT, which is an 8km region in the Karoo. In the EHT case, there partially on African soil, and using hardware and Telescope (EHT). The EHT combined signals from South Africa’s powerful new radio telescope in the are around 10 different stations (a growing number) software developed by researchers on the African several large antennas across the globe (see Figure) Northern Cape. spread across four continents with separations up to continent. to synthesise a single Earth-sized telescope. The 10,000 km. An apt comparison between MeerKAT EHT Collaboration achieved their primary objective in Objects such as PKS 2014-55 are powered by and the EHT is that of a hand-held wide-field camera April 2019 when they unveiled the first ever image of supermassive black holes which launch jets to and an electron microscope, respectively. Both are About the Authors: a black hole. vast distances. What is unusual about PKS 2014- able to image exotic radio morphologies (shapes), his image of a black hole is fundamental to 55 is that rather than having a shape dictated by but on vastly different scales. Assoc. Prof Roger Deane is the SKA Chair in Radio our understanding of the nature of gravity. the direction of these jets, it has an additional axis, Astronomy at Wits University and an Extraordinary Professor at the University of Pretoria. His research By zooming right into the ring-like emission forming an “X” on the sky. While the EHT could make out a doughnut on the T interests cover a broad range of energy and spatial scales around the black hole in a galaxy 55 million light lunar surface, MeerKAT would barely be able to tell using the power of next-generation radio telescopes such years away, we can measure the local space-time One explanation for the unusual shape of PKS Johannesburg and Pretoria apart if they were on as MeerKAT and the Event Horizon Telescope. distortion. Comparing this ring size and shape with 2014-55 is the merging of supermassive black the moon. However, MeerKAT is able to image a what different theories of gravity predict enables a holes at the centre of the “host” galaxy. Therefore, wide area of sky, detecting thousands of objects Dr Kshitij Thorat works as a postdoctoral fellow at the brand new, extreme test of this fundamental force. galaxies like these can be important signposts of simultaneously, all with superb imaging quality, albeit University of Pretoria. He finished his doctoral work at the In addition, the unparalleled sharpness of the EHT the evolutionary life-cycle of black holes, despite at a lower sharpness than the EHT. Indian Institute of Science, after which he has been based in South Africa. His research interests revolve around images, especially of the magnetic field structure, the fact that they exist on scales far larger than extragalactic radio sources: their life-cycles, morphology helps unveil how black holes launch jets at speeds that of the black holes themselves. This provides Another way you could think of the two telescopes SAAO and their impact on surroundings. close to that of light. information on how the black hole jets interact with is that MeerKAT is able to identify needles in a

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