Astronomers have published the first view of a black hole, an observation that takes science a step closer to understanding the origins of the gigantic celestial objects at the centre of galaxies.
The image of a hole at the heart of the M87 galaxy — 6bn times bigger than the sun and 53m light years away — was released on Wednesday at simultaneous press conferences around the world. It was compiled over two years using data drawn from a global network of radio telescopes, from the South Pole to Hawaii and Spain.
Heino Falcke, professor of radio astronomy at Radboud University in the Netherlands, one of the project leaders, said: “I have seen many beautiful [simulated] images of how a black hole should look . . . but seeing that very first real image, you think ‘Wow it really looks like that’. It was such an emotional moment.”
Since seeing inside a black hole is impossible, because no light or electromagnetic radiation can escape its overwhelming gravitational pull, the team focused instead on the black hole’s outer edge, or “event horizon”.
The pictures released on Wednesday show a bright ring of photons — created by light particles that would normally travel in a straight line — bent into a circular path by extreme gravity before they fall into the black hole. Inside the ring, the shadow of the hole itself can be observed.
The image would not have been achievable by any individual observatory. Over a period of two years, the Event Horizon Telescope collaboration processed radio waves detected by the eight participating telescopes that focused on M87 during a week in 2017. The data were then combined through a technique called “very-long baseline interferometry”.
Shep Doeleman of Harvard University, director of the telescope project, said: “We have achieved something presumed to be impossible a generation ago. Breakthroughs in technology, connections between the world’s best radio observatories and innovative algorithms all came together to open an entirely new window on black holes.”
Although the word “hole” suggests an empty space, the reality is the exact opposite: black holes are the densest concentrations of matter possible under the laws of physics.
After forming his theory of relativity early in the 20th century, Albert Einstein speculated about their existence. Prof Falcke confirms that the image from the Event Horizon Telescope “fits perfectly the prediction given by relativity”.
Scientists began seriously to treat black holes as real in the 1960s when they observed matter being sucked into extremely dense, dark objects. More recently, Stephen Hawking’s scientific reputation came to rest above all on his theoretical work on the nature of black holes.
The closest astronomers had previously come to a direct observation was in 2015 when a collision between two black holes allowed gravitational waves to be detected.
Most black holes are the result of ancient stars collapsing in on themselves after their supply of nuclear fuel runs out. But far larger ones form when vast quantities of material are sucked into the centre of a galaxy.
The new black hole image “is not like what we may have seen in movies like Interstellar, but all the features are there”, said Michael Kramer from the Max Planck Institute for Radio Astronomy in Germany.
“The image shows all the features you would expect from a black hole and an event horizon. You see a photon ring, you see a bright ring around the black hole and you see a shadow in the middle.
“It is quite stunning,” he added. “History books will be divided into the time before the image and after the image.”
The estimated $40m cost of the project has been met by the EU’s European Research Council, the US National Science Foundation and Asian funding agencies.
While the pictured object is a particularly monstrous example of a black hole, the next target for the telescope team is nearer to home. That is the black hole at the centre of our own Milky Way galaxy, called Sagittarius A*, which is one-thousandth the size but 1,000 times closer.
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