The first images of a black hole are a moving reminder of our collective vulnerability

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.

For years, black holes have occupied a curious place, long straddling the line between science and science fiction. They’ve been proven time and time again by models and equations, originating in 1915 with Albert Einstein’s theory of general relativity – but we’ve never been able to actually see one. This all changed on Wednesday, when an international consortium of researchers showed the world the first ever image of a black hole, over 50 million light years away.

The picture shows what looks like a flaming orange and red ring with a black circle in the middle, surrounded by darkness on all sides. This supermassive black hole sits at the centre of Messier 87, a galaxy 54 million light years away (and is one of the largest known galaxies in our universe), nested in the Virgo cluster. It has a mass 6.5 billion times that of the sun.

In a series of six papers published in the journal Astrophysical Journal Letters, the researchers detailed the process of producing these images (there were four images in total). They captured the black hole with the Event Horizons Telescope (EHT), which is a misnomer – in fact, it is eight telescopes, scattered across six continents (with contributions from over 200 scientists), forming a kind of franken-telescope that is virtually the size of the planet. Data was sifted through and stitched together using a technique called interferometry, over the course of two years, to create the images that we see today.

The picture of the black hole confirms Einstein’s theory of general relativity. He posited that time and space should be treated the same, a hypothesis that came with strange predictions, including the existence of black holes – an object so incredibly dense that space and time began to fold in on themselves. The gravitational pull of a black hole is so intense that nothing could ever escape it.

“You can understand why it’s so bizarre to say, there are these regions of our universes, where, once you cross them, you can never return,” says Dr Ziri Younsi, who works at the UCL Mullard Space Science Laboratory and was involved in the EHT imaging. “So, obviously, you have to ask, what does it look like?”

Generating an image of a black hole is a paradox. A black hole is invisible by nature – it emits no matter that we can measure. So what we see in the image is actually its event horizon. The bright ring is not a physical ring – it’s light coming from matter orbiting the black hole, which is so extremely warped that light itself is bending. There are black holes at the centre of every galaxy – some which sing, some which whir along quietly – and now that we’ve created images of one, it’s possible that we can continue to image more black holes, and even other kinds of cosmic matter.

For scientists – and for the rest of us – its significance cannot be overstated. In a press conference in Washington, Shep Doeleman, the director of the EHT, said, “We are delighted to report to you today that we have seen what we thought was unseeable.” When the image itself was revealed, there were audible gasps from audiences at press conferences around the world.

The last time that we experienced, collectively, an image like this was in the late 1960s, when astronaut William Anders took the now iconic photo of Earth from the surface of the moon in Apollo 8. While that event arguably spurred on a wave of environmental action – driven by the emotional reaction to seeing the planet that we live on for the first time – this image is valuable, and moving, in a different way.

“Black holes… represent the ultimate death and destruction,” says Dr.Younsi. “But they’re also the heart of galaxies – they power everything in them.” Space has always played a particular role in the public imagination – at once omnipresent and also unknowable, images from the International Space Station, of the moon landing, even of Mars are often of interest to the general public.

In Annie Dillard’s seminal essay about her experience of watching a total eclipse, she writes that the experience of the eclipse was like coming into contact with the universe that we had read so much about and never before felt. “How could anything moving so fast not crash, not veer from its orbit, amok like a car out of control on a turn?” she asks.

Coming into contact with this black hole feels a little like that. Looking at an image of the black hole may fill you with a vague sense of unease and dread, reminding you of how little we really know of the universe that we live in (as is evident from social media, this feeling is fertile ground for memes).

For researchers hoping to further crack open the cosmos, this leaves the door open for all kinds of future discoveries, ones which might seem impossible now. “Our capability is limited by the size of the Earth,” adds Dr Younsi. “So yes, we might have to build telescopes which are bigger than it, or put instruments on other planets, but this is only the beginning.”