“By averaging them together, we are able to emphasize common features,” says EHT member José Gómez, at the Institute of Astrophysics of Andalusia in Granada, Spain. “Sagittarius A* varies on time scales of 5 to 15 minutes.”īecause of this variability, the EHT team generated not one image of Sagittarius A*, but thousands - and the image unveiled today is the result of a lot of processing. “In M87*, we saw very little variation within a week,” says Heino Falcke, an astrophysicist at Radboud University in Nijmegen, the Netherlands, and a co-founder of the EHT collaboration. But Sagittarius A* can change quickly, even over the few hours that the EHT observes it every day. Any blobs of matter spiralling around M87* are covering much larger distances - larger than Pluto’s orbit around the Sun - and the radiation they emit is essentially constant over short time scales. The two black holes have roughly the same apparent size in the sky, because M87* is nearly 2,000 times farther away but about 1,600 times larger. The EHT researchers unveiled their image of M87* in 2019, showing the first direct evidence of an event horizon, the spherical surface that shrouds a black hole’s interior.īut the Sagittarius A* data were more challenging to analyse. They collected nearly 4 petabytes (4,000 terabytes) of data, which was too much to be sent over the Internet and had to be carried by aeroplane on hard disks. The observatory locations ranged from Spain to the South Pole and from Chile to Hawaii. “I mean, what’s more cool than seeing the black hole at the centre of the Milky Way?” Black-hole observationsĭuring five nights in April 2017, the EHT collaboration used eight observatories across the world to collect data from both the Milky Way’s black hole - called Sagittarius A*, after the constellation in which it is found - and M87*, the one at the centre of the galaxy M87.īlack hole pictured for first time - in spectacular detail “We’ve been working on this for so long, every once in a while you have to pinch yourself and remember that this is the black hole at the centre of our Universe,” said EHT team member Katie Bouman, a computational-imaging researcher at the California Institute of Technology in Pasadena, at a press conference in Washington DC. The team published its results in a special issue of The Astrophysical Journal Letters 1. “Today, right this moment, we have direct evidence that this object is a black hole,” said Sara Issaoun, an astrophysicist at the Harvard and Smithsonian Center for Astrophysics in Cambridge, Massachusetts, at a press conference in Garching, Germany. The long-awaited results, presented today by the Event Horizon Telescope (EHT) collaboration, show an image reminiscent of the earlier one: a ring of radiation surrounds a darker disk of precisely the size that was predicted from indirect observations and from Albert Einstein’s general theory of relativity. It is only the second-ever direct image of a black hole, after the same team unveiled a historic picture of a more distant black hole in 2019. Radioastronomers have imaged the supermassive black hole at the centre of the Milky Way. Credit: Event Horizon Telescope collaboration The second-ever direct image of a black hole - Sagittarius A*, at the centre of the Milky Way.
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