![]() Instead, observers save the information to hard drives and physically fly them to sites in Germany and Massachusetts, where the data are correlated, perfectly synched within trillionths of a second. These data can’t simply be emailed (imagine that error message!). Reconstructing the shadow’s image required collecting incredible amounts of data - 3½ petabytes in this case, the equivalent of 100 million TikTok videos, quipped Vincent Fish (MIT Haystack Observatory) during the press conference. The Event Horizon Telescope Collaboration / Astrophysical Journal Letters 930:L12, 2022 May 10 Check out our VLBI primer for more details. These changes help to fill in the virtual dish observing the black hole. As the planet turns, each telescope's view of the galactic center changes, and the dishes' apparent separations as seen from the black hole's perspective change, too. The 2017 Event Horizon Telescope observations used eight radio telescopes at six locations spread across the globe. To even begin to fill in the image we’re trying to see, we need a variety of baselines, and more is definitely better. ![]() Each pair’s distance, or baseline, probes a different scale: Long baselines tell us about the fine structure of the object observed, whereas short baselines tell us about the big features. The key with VLBI, however, is not just having a single big virtual dish. This technique, called very long baseline interferometry (VLBI), combines the data from pairs of telescopes to achieve the resolution that would be possible if we had a radio dish as large as the distance between them. They used eight radio telescopes at six sites, spread from Arizona to the South Pole and Hawai‘i to Spain, to create a planet-size virtual telescope. Astronomers observed Sgr A* over five nights in April 2017, during the same observing run that brought us the M87* image. More than 300 people, working at 80 institutions in various countries, contributed to making this image a reality. Scientists with the Event Horizon Telescope (EHT) created the image by combining data from eight radio observatories across the planet to form a single “Earth-sized” virtual telescope.ĮHT Collaboration How to Take a Black Hole’s “Photo” ![]() It’s the first direct visual evidence of the presence of this black hole. This is the first image of Sgr A*, the supermassive black hole at the center of our galaxy. This was the moment so many of us had waited for: We have finally met our black hole face to face. When EHT astrophysicist Feryal Özel (University of Arizona) unveiled Sgr A*’s image in D.C., the room burst into applause. The light is radio emission and comes from electrons in the gas that swirls around the black hole the dark center is where light comes too close to Sgr A* and plunges past the event horizon, never reaching us and leaving a “shadow” where the black hole is. Just like the iconic 2019 image of the black hole at the center of the elliptical galaxy M87, Sgr A*’s image shows a fuzzy ring of light encircling a dark center. Today, however, is the first time that we can see the black hole - or, rather, its silhouette. They’ve watched stars whiz around on orbits that revealed the invisible object’s mass and caught flares as the gas trickle lit up. Astronomers have spent decades edging closer to the black hole’s event horizon, that infamous point of no return. The infalling gas emits only a few hundred times as much energy as our Sun, so at 26,000 light-years away, Sgr A* is anything but bright.īut it’s also the closest supermassive black hole to Earth, and it’s our galaxy’s dark heart, making it an irresistible target. Sgr A* is a “gentle giant” among black holes, grazing on a thin trickle of gas that reaches it from the winds of stars clustered in the galactic center. That black hole, Sagittarius A*, packs the mass of 4 million Suns into a region smaller than Mercury’s orbit around our star. Today at multiple press conferences given simultaneously around the world, scientists with the Event Horizon Telescope project unveiled the first image of the black hole at the heart of our galaxy.
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