Just over a week ago, on Wednesday, April 10th, The Event Horizon Telescope Collaboration had some exciting news to share with the world - they had captured and created the very first actual image of a black hole. It’s said that “seeing is believing”, and that’s why this image has caused so much excitement. The image gives us visual evidence that supports the theory that black holes, as scientists suspect, actually exist!

Black holes themselves are invisible, so the closest astronomers can get to an image of a black hole is to capture its shadow. The revolutionary image shows a circular object, a halo of dust and gas, surrounding the black centre of the hole itself.

The massive black hole is located in the centre of a galaxy known as Messier 87, or just M87, and is thought to be one of the largest black holes viewable from Earth. This black hole resides 55 million light years from Earth and its mass is 6.5 billion times the size of our sun.

But what really is a black hole? A simple way to define it is to say that a black hole is a region in space where the gravitation is so strong that nothing can escape, not even light. The surface around the black hole where there is no return, is called the event horizon. The object is so dense that it sucks up everything that ventures too close, and this makes the actual black hole itself completely black, or invisible in space.

A stellar black hole is formed when a star dies and causes an explosion, supernova, where parts of the star blasts out in space while some of it get compressed into a tiny space, the black hole. There are also thought to exist primordial black holes that formed right after the Big Bang, though how a supermassive black hole like the one in the middle of M87 is formed, remains open for further research. Astronomers believe to have found evidence that a massive black hole exists in the middle of almost all galaxies, and that it is likely they were formed at the same time as the galaxy they are in.

The image was captured by The Event Horizon Telescope Collaboration (EHT), which is a global network of telescopes. In 2008 a small group of only 25 people started this project, but now after a decade it has grown to a collaboration of about 200 scientists across the globe. New technology had to be invented to make it possible to take a photo of an object so far from Earth, and everyone from students to senior scientists have worked together to make this image become reality.

To be able to collect the information they needed, they combined eight telescopes placed around the world which then created a virtual telescope about the size as Earth itself. In order for this to work out, they were dependent on good weather simultaneously in all those eight places around the world. They were really fortunate to actually have the weather on their side for the whole two weeks they needed to collect the data, which happened in April 2017. The telescopes each collected light from around the black hole, which was supposed to give the researchers an indication of the structure of the black hole. The information from each of the telescopes was stored on massive hard drives that were flown to where specialised computers, correlators, where placed, and those combined the data. Since they were only using a few telescopes scattered around the earth, there are some parts missing in the constructed image, so they had to use calculated algorithms with the information they got from the telescopes to construct the full image.

Another photo that has been circling the internet for the past week is that of a young woman full of excitement. Her name is Katie Bouman, a computer scientist and one of those behind one of the key pieces in this project; the algorithm that constructed the revolutionary image of a black hole.

When Bouman spoke about this project at a TED event in 2016, she described how they hoped to be able to fill in the gaps between the eight telescopes placed around the Earth by using the fact that Earth is spinning to their advantage. This making each telescope covering a bigger part of the earth sized telescope they aimed to create, and thus collect more data for the finished image. But even then they still had not filled in all gaps completely, which is where Katie’s job came in to play. By using pixels from lots of different already existing photos of everything from other space objects to everyday photos from life here on Earth, her job was to make the algorithm use the photo pixels and the light information from the telescopes to construct different images. But because a black hole has never actually been observed until now, they couldn’t know if black holes actually look like what science suspects, and as she humorously said, they wanted to still keep the option open of there to be a big elephant floating in space. Because there still were a few gaps in the data the telescopes collected, many different constructed images could fit the criterias, and the algorithm therefore also had to be able to choose the most likely ones to be the black hole and hope that the image they managed to find looked similar to the animations created based on the science done on black holes.

And now we can finally see the result of this huge project. The blurry image is a big step in how we can understand space, and because seeing is believing, we can now be even more certain that black holes actually exist!