But they still needed good weather at all eight of their telescope sites to see the black hole. The gas emits light of all different wavelengths, including visible light, but the researchers chose this particular wavelength because it can sail through entire galaxies and even Earth’s own atmosphere without being absorbed. To see the black hole’s boundary between light and dark, the astrophysicists captured radio waves-light 1.3 millimeters in wavelength, invisible to the human eye-emitted by the gas swirling around the black hole. “It’s like going from a cheap smartphone camera to a high definition IMAX cinema,” says astrophysicist Andrew Strominger of Harvard University, who was not involved in the work. Previously, researchers had captured a blobby jet of light emerging from where the M87 black hole was predicted to be-but they couldn’t definitively see the black hole because their instruments were nowhere near as sharp as EHT’s. In the image, it manifests itself as the “sudden absence of light,” she says. “It’s the point of no return,” says Feryal Özel of the University of Arizona, who is a member of the EHT collaboration. The event horizon is the edge of the spacetime abyss, where gravity is so strong that no light can escape from it. Past the bright lights, though, is the black hole’s telltale feature: its event horizon. The picture, taken over five days of observations in April 2017 using eight telescopes around the world by a collaboration known as the Event Horizon Telescope, depicts luminous gas swirling around a supermassive black hole at the center of M87, a galaxy 54 million light-years away. On Wednesday, astrophysicists announced they had captured the first-ever image of a black hole. But they’d never glimpsed a black hole face to face-until now. They’ve heard the vibrations, or gravitational waves, resonating from black holes colliding. They’ve observed the push and pull of black holes on the orbits of nearby stars and planets. In the century since Einstein predicted the existence of black holes in his theory of gravity, astrophysicists have turned up overwhelming evidence for the things.
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