First-ever photo of a black hole released
It is 6.5 billion times more massive than the Sun, and it is 55 million light years away.
This is the first photo ever to be taken of a black hole - an area in space with a gravitational field that so strong, nothing can escape from it.
Black holes gobble up anything in their vicinty, even light. That means they have never been particularly easy to photograph. But the Event Horizon Telescope (EHT), a network of linked radio telescopes, has finally managed it.
Sheperd Doeleman, Event Horizon Telescope Director, told The Guardian, 'Black holes are the most mysterious objects in the universe. We have seen what we thought was unseeable. We have taken a picture of a black hole.'
This black hole is in the middle of a distant galaxy called Messier 87, about 55 million light years away from Earth. It has a mass 6.5 billion times that of the Sun.
Capturing it took a truly global effort from hundreds of scientists. Eight telescopes had to point at the black hole simultaneously - effectively creating an 'Earth-sized telescope'. They were stationed at different locations all over the world, including on volcanoes in Hawaii and Mexico, mountains in Arizona and the Spanish Sierra Nevada, the Chilean Atacama Desert, and Antarctica.
Six papers published today in the Astrophysical Journal Letters describe how this image came to be.
What is a black hole?
Black holes are created when huge amounts of matter is packed into a very small space. This density creates a gravitational field so powerful that nothing can escape its pull. Many of them form in the aftermath of a large star's death.
The sizes of black holes can vary. The biggest are called supermassive black holes, and these have a mass greater than one million suns. Evidence suggests that every large galaxy contains a supermassive black hole at its center, which influences how that galaxy is formed and grows.
Supermassive black holes may sound pretty big, but they are actually relatively small in the grand scheme of the universe.
Photographing the invisible
Black holes are invisible, but scientists know they are present because of the effect they have on other things in a galaxy. They can warp spacetime, and heat material near to them.
Their lack of light has made them difficult to study - and very difficult to document. For a long time, it was thought that capturing them on camera would be an impossible ask.
Each telescope in this project created huge amounts of data - roughly 350 terabytes per day. This data was all pulled together using highly specialised supercomputers at the Max Planck Institute for Radio Astronomy and MIT Haystack Observatory.
It was then painstakingly converted into an image.
The EHT team said that their imaging methods revealed a bright, ring-like structure with a dark central region - the black hole’s shadow. The ring is caused by light bending in the intense gravity.
Taking a photo of a black hole's shadow is the closest we can come to photographing the black hole itself.
Chair of the EHT Science Council, Heino Falcke, says, '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.
'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.'