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What was only science fiction until now, or theory at best, was confirmed as being a reality on April 10, 2019. At six simultaneous press conferences around the world, scientists from the “Event Horizon Telescope” unveiled the first image of a black hole. Exactly 100 years after Albert Einstein described the existence of black holes in his General Theory of Relativity, we now have the first proof that he was right: Black holes do exist and they look exactly as previously assumed.

The Event Horizon Telescope (EHT) – an array of eight ground-based radio telescopes forged through international collaboration — was specially designed to capture images of a black hole. The individual telescopes are located at places such as volcanoes in Hawaii and Mexico, the mountains in Arizona, the Spanish Sierra Nevada, the Chilean Atacama Desert, and the Antarctic. The image of a supermassive black hole and its shadow published today is 55 million light years from Earth, at the heart of the galaxy Messier 87H in the nearby Virgo galaxy cluster. It has a mass 6.5 billion times that of the Sun.

According to ESO, the EHT virtual telescope offers scientists a new way to study the most extreme objects in the universe, predicted and now confirmed by Einstein’s General Theory of Relativity in the centenary year of the historic experiment that first confirmed the theory. “We have taken the first picture of a black hole,” said EHT project director Sheperd S. Doeleman of the Center for Astrophysics | Harvard & Smithsonian. “This is an extraordinary scientific feat accomplished by a team of more than 200 researchers.”

black hole
Anatomy of a black hole © ESO

Predicted by Einstein’s General Theory of Relativity

Black holes are cosmic phenomena with an enormous mass that absorb everything that comes close to them, even light. These objects affect their environment in extreme ways, warping spacetime and superheating any surrounding material. “If immersed in a bright region, like a disc of glowing gas, we expect a black hole to create a dark region similar to a shadow — something predicted by Einstein’s general relativity that we’ve never seen before,” explained chair of the EHT Science Council Heino Falcke of Radboud University, the Netherlands. “This shadow, caused by the gravitational bending and capture of light by the event horizon, reveals a lot about the nature of these fascinating objects and has allowed us to measure the enormous mass of M87’s black hole.”

Thanks to several calibration and imaging methods, the image shows a ring-like structure with a dark central region — the black hole’s shadow. “Once we were sure we had imaged the shadow, we could compare our observations to extensive computer models that include the physics of warped space, superheated matter, and strong magnetic fields. Many of the features of the observed image match our theoretical understanding surprisingly well,” remarks Paul T.P. Ho, EHT Board member and Director of the East Asian Observatory. “This makes us confident about the interpretation of our observations, including our estimation of the black hole’s mass.”

EHT board member Luciano Rezzolla of the Goethe University in Frankfurt am Main continued: The confrontation of theory with observations is always a dramatic moment for a theorist. It was a relief and a source of pride to realize that the observations matched our predictions so well.”

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Picture of Messier 87 with the Very Large Telescope © ESO

Reading a newspaper in New York from a café in Paris

According to ESO, the EHT observations, use a technique called very-long-baseline interferometry (VLBI), which synchronizes telescopes around the world and exploits the rotation of our planet to form a huge, Earth-size spanning telescope observing at a wavelength of 1.3mm. “VLBI allows the EHT to achieve an angular resolution of 20 micro-arcseconds — enough to read a newspaper in New York from a café in Paris ”

The sensational image of the black hole represents the culmination of decades of observational, technical, and theoretical work by researchers from around the world, including the ESO and the Max Planck Institute for Radio Astronomy.

“ESO is delighted to have significantly contributed to this result through its European leadership and pivotal role in two of the EHT’s component telescopes, located in Chile — ALMA and APEX. ALMA is the most sensitive facility in the EHT, and its 66 high-precision antennas were critical in making the EHT a success,” commented ESO Director General Xavier Barcons. “We have achieved something presumed to be impossible just a generation ago,” concluded Doeleman. “Breakthroughs in technology, connections between the world’s best radio observatories, and innovative algorithms all came together to open an entirely new window on black holes and the event horizon.”

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