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First image of a black hole


This black hole resides 55 million light years from Earth and has a mass 6.5 billion times that of the sun

Picture: Event Horizon Telescope Collaboration

THE FIRST ever image of a supermassive black hole, and its shadow, has been published.

The Event Horizon Telescope (EHT) – a planet-scale array of eight ground-based radio telescopes forged through international collaboration – was designed to capture images of a black hole.

This week, EHT researchers revealed that they have succeeded, unveiling the first direct visual evidence of a supermassive black hole and its shadow.

The South African Radio Astronomy Observatory (SARAO) yesterday congratulated the EHT Consortium on capturing the first image of the gargantuan black hole at the heart of the distant galaxy Messier 87.

The image reveals the black hole at the centre of Messier 87, a massive galaxy in the nearby Virgo galaxy cluster.

This black hole resides 55 million light years from Earth and has a mass 6.5 billion times that of the sun.

The EHT links telescopes around the globe to form an Earth-sized virtual telescope, using the same technique as the African Very Long Baseline Interferometry (VLBI) Network, but at much higher frequency, enabling an even sharper view of black holes.

The EHT is the result of years of international collaboration and offers scientists an unprecedented view of supermassive black holes, which are of the most extreme objects in the universe.

Supermassive black holes are a prediction of Einstein’s General Theory of Relativity theory and this first image of the black hole shadow has been announced during the centennial year of the historic experiment that first confirmed his theory.

“We have taken the first picture of a black hole,” EHT project director Sheperd S Doeleman of the Center for Astrophysics Harvard & Smithsonian, said.

“This is an extraordinary scientific feat accomplished by a team of more than 200 researchers.”

Black holes are extraordinary cosmic objects with enormous masses but extremely compact sizes. The presence of these objects affects their environment in extreme ways, warping spacetime and super-heating any surrounding material.

“If immersed in a bright region, like a disc of glowing gas, we expect a black hole to create a dark region similar to a shadow – something predicted by Einstein’s general relativity that we’ve never seen before,” explained chair of the EHT Science Council Heino Falcke of Radboud University, the Netherlands.

“This shadow, caused by the gravitational bending and capture of light by the event horizon, reveals a lot about the nature of these fascinating objects and allowed us to measure the enormous mass of M87’s black hole.”

Multiple calibration and imaging methods have revealed a ring-like structure with a dark central region – the black hole’s shadow – that persisted over multiple independent EHT observations.

“Once we were sure we had imaged the shadow, we could compare our observations to extensive computer models that include the physics of warped space, super-heated matter and strong magnetic fields. Many of the features of the observed image match our theoretical understanding surprisingly well,” Paul TP Ho, EHT board member and director of the East Asian Observatory,” remarked.

“This makes us confident about the interpretation of our observations, including our estimation of the black hole’s mass.”

The EHT collaboration involves more than 200 researchers from Africa, Asia, Europe, and North and South America.

This includes Professor Roger Deane from the Department of Physics at the University of Pretoria, as well as his post-doctoral fellow, Dr Iniyan Natarajan, from the Department of Physics and Electronics at Rhodes University in Makhanda. Their contribution was to build a highly realistic simulation of this Earth-sized instrument that enables astronomers to better understand real observations, discriminate between theoretical black hole models, and provide insights into the characteristics of the telescope itself.

“I am extremely proud of the young team that has contributed to this historic result,” said Deane. “The result and new techniques developed by the EHT Consortium highlight the power of creating continental or Earth-sized telescopes and the great discoveries it can enable.”

The shadow of a black hole is the closest the consortium could come to an image of the black hole itself, a completely dark object from which light cannot escape. The black hole’s boundary – the event horizon from which the EHT takes its name – is around 2.5 times smaller than the shadow it casts and measures just under 40 billion km across.

Supermassive black holes are relatively tiny astronomical objects – which has made them impossible to directly observe until now. As a black hole’s size is proportional to its mass, the more massive a black hole, the larger the shadow. Thanks to its enormous mass and relative proximity, M87’s black hole was predicted to be one of the largest viewable from Earth — making it a perfect target for the EHT.