It took eight radio observatories around the world, and that network has already expanded to 11 today, many built, funded, operated and supported through international organisations across many countries around the world.” Xavier Barcons, director general of the European Southern Observatory, spoke at the press conference: “This extraordinary result would not have been possible to achieve by one single facility or even the national astronomical community of a single country. This means the brightness and pattern of the gas around Sgr A* were changing rapidly as the EHT Collaboration was observing it – a bit like trying to take a clear picture of a puppy quickly chasing its tail.” “But where gas takes days to weeks to orbit the larger M87*, in the much smaller Sgr A* it completes an orbit in mere minutes. “The gas in the vicinity of the black holes moves at the same speed – nearly as fast as light – around both Sgr A* and M87*,” says Chi-kwan Chan, an EHT scientist based at the University of Arizona, US. Credit: EHT collaboration (acknowledgment: Lia Medeiros, xkcd). Sgr A* is 4.1 million times the mass of our Sun and sits at the centre of our own Milky Way galaxy. M87* is 6.5 billion times the mass of our Sun and located in the heart of galaxy Messier 87. A size comparison of the two black holes imaged by EHT. So, imaging Sagittarius A* clearly is not easy work. Comparatively, matter orbits M87* over the course of days. This is because Sagittarius A* is constantly changing with matter orbiting it in a matter of minutes. Though captured at the same time, the image of Sagittarius A* took longer to complete than the image of M87*. “After a number of quite complex data analysis steps, this results in the high-resolution image of the radio source.” After observations, the data are shipped to processing centres where they are combined in supercomputers. “At each telescope, the data are recorded on hard disks and are accurately time tagged by precise atomic clocks. “While the Earth is rotating, all telescopes observe the same astronomical object for several hours,” explains Thomas P Krichbaum, of Germany’s Max Planck Institute, at a press conference to announce the findings. The bright orange ring in the image is the matter swirling around the black hole, and the dark shadow in the middle is the black hole itself. The EHT detects radio frequencies to create the image of Sagittarius A*. Referred to as an “Earth-sized telescope,” the EHT links together 11 telescopes around the world, effectively creating one telescope with a mirror the size of the Earth. More than 300 astronomers, and hundreds of engineers and support staff from 60 institutions across 20 countries and regions, processed data from a 2017 observation of Sagittarius A*. More on astronomy: Compare the pair: James Webb telescope MIRI provides images of unprecedented quality Despite being four million times more massive than our Sun, Sagittarius A* is still about 1000 times smaller than the M87 supermassive black hole. Sagittarius A* lies in the centre of the Milky Way 26,000 lightyears away from Earth and can be seen in the night sky as part of the Sagittarius constellation. The release of the picture is the latest in a series of developments in our knowledge of these elusive and mysterious objects – and come three years after the imaging of the supermassive black hole in the centre of the Messier 87 galaxy (M87*). The imaging of the supermassive black hole, named Sagittarius A* (Sgr A*), provides strong evidence to support the 60-year-old theory that a supermassive black hole lurks at the centre of the Milky Way. On Thursday last week, NASA’s Event Horizon Telescope (EHT) captured the first ever image of the supermassive black hole at the centre of our galaxy.
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