While the researchers focused on M87 for this image, the overall EHT project also has plans to try and produce an image of the black hole at the Milky Way’s galactic centre, called Sagittarius A*. ‘It’s confirmation that one of the most fundamental predictions (of general relativity) has passed the test.’ ‘Of course we would have loved to prove Einstein wrong, but everything we see fits perfectly the prediction that is given by general relativity,’ said Dr Heino Falcke from Radboud University Nijmegen in the Netherlands, also a principal investigator on BlackHoleCam. We can also see that the boundary between the interior and exterior of the black hole – the event horizon – actually exists, with a ring of photons of light surrounding it. The shadow of the black hole is proof that its gravity is so intense that it is bending light itself, a prediction made thanks to general relativity. Never before, however, have we actually seen a black hole.Īnd the image of M87’s black hole matches our predictions for what it should look like. We have also detected gravitational waves – ripples in space-time formed by two black holes merging. We have seen regions of super-heated material swirling around suspected black holes, known as quasars, and we have seen stars orbiting the black hole believed to be at the centre of our own galaxy. Since then we have found indirect evidence for black holes. It was suggested that if an object’s mass reached astonishingly high levels, it would collapse in on itself into a singularity, a point in space and time where gravity is so intense that the known laws of physics break down. The existence of black holes was first proposed following Albert Einstein’s general theory of relativity in 1915. It took the astronomers until summer 2018 to actually put the final image together. It had to be physically transported by sea and air before image processing could take place. Using a technique called very-long-baseline interferometry (VLBI), the teams then combined the observations of the telescopes to give the final image.īut so much data was collected – 4 petabytes, or 4 million gigabytes – that it could not be digitally transferred. Observations of the black hole at the heart of M87 were taken over a window of 10 days in April 2017, when fortuitously good weather allowed the telescopes to continuously observe the object. ‘Of course we would have loved to prove Einstein wrong, but everything we see fits perfectly the prediction that is given by general relativity.’ Dr Heino Falcke, Radboud University Nijmegen, Netherlands ‘We have collected (information) and built an image that we believe is consistent with what we would expect from a black hole.’ ‘We observed with (eight telescopes) simultaneously, so that as Earth rotates, there are three or four that are always pointing to the (black hole),’ said Dr Luciano Rezzolla from Goethe University Frankfurt in Germany, another principal investigator on BlackHoleCam. Instead, the EHT project combined the power of eight large radio telescopes around the world, from the South Pole to Spain, to create an Earth-sized virtual super telescope. No telescope alone possesses the observational power to observe the supermassive black holes believed to be at the centre of all galaxies. That is one of the reasons such an image has never been taken before. Seeing this event horizon is no mean feat the black hole itself, while 6.5 billion times more massive than our Sun, is still incredibly small at this distance. The image shows the shadow of the event horizon around the supermassive black hole inside Messier 87 (M87), an elliptical galaxy located 53 million light-years from Earth. ‘It is the first time that this has been possible, and it’s been long in the making.’ ‘History books will be divided into the time before the image and after the image,’ said Dr Michael Kramer from the Max Planck Institute for Radio Astronomy in Germany, one of the principal investigators on BlackHoleCam, the European contribution to the EHT. It is the first time in history that such an image has been produced and was the result of a global collaboration of scientists working on the Event Horizon Telescope (EHT) project. The image shows the event horizon – the gravitational point of no return beyond which nothing, not even light, can escape – around the supermassive black hole in a nearby galaxy.
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