Alex Rose-Innes
Since Albert Einstein predicted black holes more than a century ago, scientists have worked towards imaging the event horizon (the surface of a black hole), million times smaller than a pinprick.
The breakthrough role of EHT
Now the first proper images of the black hole at the centre of our galaxy, the Milky Way, had been produced by the Event Horizon Telescope (EHT) Collaboration, a global team of 300 scientists, including two from the African continent both from South Africa. The University of Pretoria’s Roger Deane had been instrumental in publishing the latest findings in two papers in The Astrophysical Journal Letters. The other South African scientists involved in what is termed as a milestone, is The University of the Witwatersrand (Wits) postdoctoral researcher, Iniyan Natarajan.
The EHT links a network of eight telescopes from around the world to produce a virtual Earth-sized telescope, allowing researchers to measure the equivalent of a mobile phone lying on the moon’s surface. According to collaborating scientist Andrew Chael, a Princeton/Nasa Hubble Fellow, the new images are keys to understanding how magnetic fields allow black holed to consume matter and launch powerful jets.
The EHT links a network of eight telescopes from around the world to produce a virtual Earth-sized telescope, allowing researchers to measure the equivalent of a mobile phone lying on the moon’s surface.
The image of Sagittarius A* was enabled by an engineering breakthrough and expertise developed in preparation for the world’s largest radio telescope, the Square Kilometre Array (SKA) on South African soil.
The first time an image had been captured, though not in our Milky Way, was in 2019 – at the centre of a different galaxy, Messier 87, which is 55 million light years away.
Imaging of Sagittarius A* and its importance
It is so much more than a mind-blowing image, but led to a myriad of new scientific results, published in ten journals. Not only does it prove beyond any doubt Einstein’s General Theory of Relativity, it also shows how two different black holes can differ in mass by a factor of over 1000.
Earlier research over three decades showed strong evidence that galaxies and their black holes co-evolve over cosmic time and this latest image allowed scientists to understand the relationship between these black holes and host galaxies.
Southern Africa’s (SA) geographic advantage
With a joint Dutch-Namibian initiative and SKA, it is expected that SA’s geographic advantage could play a critical role in the future of breakthrough black hole movies. For Africa, it is a unique opportunity to showcase its scientific talent. Already, SA had been instrumental in paleo-anthropology with contributions to global astronomy which can only be made from SA soil. As Sagittarius A* lies in the southern sky, it passes directly above the country, a major reason why this latest image of the Milky Way’s centre, taken by the MeerKAT (a precursor to the SKA) is lauded as the best ever.
The MeerKAT Galactic Centre image (top). While the left image is only a simulation, the image in the middle had been produced by using an African-enhanced EHT array.
The future of African space performance
SA’s well-established astronomical site infrastructure is protected by legislation. With world-class engineers at the forefront of their craft, it is ideal for low-cost, high-performance telescopes. Also, with new state-of-the-art simultaneous multi-frequency receiver design, EHT sites no longer need to be the most pristine, high-altitude locations on Earth.
This provides for a dramatic increase in the number of young Africans who participate in this new era of black hole imaging and precision tests of gravity. It is predicted that in the future, new findings would not be possible without technology on SA soil. It is also expected that South African scientists would be leading high-impact, high-visibility EHT science in synergy with multi-wavelength astronomy and high-energy astrophysics programmes.
