DAA Daily

How exactly was the black hole image captured?

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. In coordinated press conferences across the globe, EHT researchers revealed that they succeeded, unveiling the first direct visual evidence of the supermassive black hole in the centre of Messier 87 and its shadow. The shadow of a black hole seen here is the closest we can 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. While this may sound large, this ring is only about 40 microarcseconds across — equivalent to measuring the length of a credit card on the surface of the Moon. Although the telescopes making up the EHT are not physically connected, they are able to synchronize their recorded data with atomic clocks — hydrogen masers — which precisely time their observations. These observations were collected at a wavelength of 1.3 mm during a 2017 global campaign. Each telescope of the EHT produced enormous amounts of data – roughly 350 terabytes per day – which was stored on high-performance helium-filled hard drives. These data were flown to highly specialised supercomputers — known as correlators — at the Max Planck Institute for Radio Astronomy and MIT Haystack Observatory to be combined. They were then painstakingly converted into an image using novel computational tools developed by the collaboration.

By Maya Hariz

Staff Reporter

The Pawprint

What is shown in the image above is the first direct picture of the black hole. Many may say that the black hole doesn’t quite look as people would have anticipated, but keep in mind that black holes by their nature are invisible.

Because of their gravitational pull is so strong that not even light can escape them. So for many years, astronomers thought that an image like this was impossible.

The photography process started with a small team of innovators and ended with a telescope that’s unlike anything anyone has seen before. Despite the major advances made in the telescope industry, there was no telescope on Earth that had the ability to take a picture of a black hole.  

The problem was that all of the telescopes were too small. The solution to that problem: 8 telescopes stationed at different points across the Earth, kept all in sync with powerful atomic locks. They call the resulting product the “Event Horizon Telescope”.

This series of telescopes, combined, have about the same capabilities as a telescope as large as our entire planet. And for the first time in history, it has shown us what a black hole around 55 million light-years away looks like. It’s about 6.5 billion times as massive as our Sun. As far as experts can tell, it looks exactly like what Einstein’s had predicted.

The light you see in the image is what is called the accretion disk. It’s a disk of light that forms around the black hole when a star travels too close and is broken apart in the process. That dark circle in the center measures 25 billion miles across.

As Stephen Hawking said, “Einstein was wrong when he said, ‘God does not play dice.’ Consideration of black holes suggests, not only that God does play dice, but that he sometimes confuses us by throwing them where they can’t be seen.”

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