Scientists have unveiled the first ever picture of a black hole, which comes from data collected by the Event Horizon Telescope (EHT) - an international project that connects dozens of observatories to capture the first image of a black hole by essentially creating a 'virtual Earth-sized telescope'.
At six major news conferences held simultaneously across the globe in Brussels, Lyngby, Santiago, Shanghai, Tokyo, Taipei and Washington, scientists revealed the first results of the EHT.
Carlos Moedas, European Commissioner of Research, Science and Innovation, said at the conference in Brussels: "If there's a big moment for all of us, it is today."
The press conference in Brussels. Credit: European Southern Observatory
"We have accomplished something many thought impossible by imaging the shadow of a black hole and it provides the strongest evidence to date that such evasive and enigmatic entities do indeed exist," said Dr Ziri Younsi (UCL Mullard Space Science Laboratory), part of the EHT project.
"You could never actually see a black hole but because it is so powerful you can see when matter starts to fall into it, getting closer and closer.
"I was amazed to see the image. I got a sense of tremendous excitement. It's something we have been working on for 10 years and actually the image was surprisingly unsurprising. Einstein's theory of general relativity predicted an image like this."
Younsi continued: "Black holes are such mysterious objects. They represent a point of the universe which is really also the edge of time. If you dropped a torch into one you would see the light extend forever getting dimmer and dimmer but taking an infinite time to reach the event horizon."
For hundreds of years, physicists have hypothesised about black holes, having first speculated about 'dark stars' in the 1700s.
"More than 50 years ago, scientists saw that there was something very bright at the centre of our galaxy," Dr Paul McNamara, an astrophysicist at the European Space Agency, told AFP.
"It has a gravitational pull strong enough to make stars orbit around it very quickly - as fast as 20 years."
Astronomers eventually began to realise the bright spots were in fact black holes (a term coined in the 1960s).
The image of the black hole
A black hole's event horizon is the point of no return, beyond which anything gets swallowed up - including stars, planets, gas, dust and even electromagnetic radiation.
"The event horizon is not a physical barrier, you couldn't stand on it," McNamara explained.
"If you're on the inside of it, you can't escape because you would need infinite energy. And if you are on the other side, you can - in principle."
According to NASA, a black hole is a 'place in space where gravity pulls so much that even light cannot get out'.
"The gravity is so strong because matter has been squeezed into a tiny space," NASA says.
"This can happen when a star is dying.
"Because no light can get out, people can't see black holes. They are invisible.
"Space telescopes with special tools can help find black holes. The special tools can see how stars that are very close to black holes act differently than other stars."
Instead, what astronomers required was the EHT, the global project that proved to be the first of its kind by connecting radio telescopes in locations including Chile, Hawaii, Arizona, Mexico, Spain and the South Pole.
"Instead of constructing a giant telescope - which would collapse under its own weight - we combined several observatories as if they were fragments of a giant mirror," Michael Bremer, an astronomer at the Institute for Millimetric Radio Astronomy in Grenoble, told AFP.