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Last April, with an event as epic as the Apollo 11 landing on the Moon, the world saw its first image of what was once purely theoretical, a black hole in the heart of the galaxy M87 the size of our solar system . and bigger, with the mass of six and a half billion suns captured by a lens the size of planet Earth and 4,000 times more powerful than the Hubble Space Telescope.
Astronomers have hypothesized that the galaxy that houses the black hole has reached its massive size by merging with several other black holes in the M87 elliptical galaxy, the largest and most massive of the near universe that would have been formed by the merger of about 100 people. small galaxies. The large size and relative proximity of the black hole in the M87 has led astronomers to think it might be the first black hole they could actually "see".
The black hole that we can now see is frozen in the time that it was 55 million years ago, because it is so far that the light took so long to reach us. "Over these centuries, we have emerged on Earth with our myths, differentiated cultures, ideologies, languages and diverse beliefs," says Columbia University astrophysicist Janna Levin.
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The Event Horizon telescope, which has imaged the black hole, actually consists of 10 telescopes connected between four continents: the United States, Mexico, Chile, Spain and Antarctica, designed to scan the cosmos on radio waves. For a few days in April 2017, the observatories studied the sky in tandem, creating a gigantic telescope of the size of the planet.
"A medium sized galaxy has crossed the center of M87 and, as a result of the huge gravitational tidal forces, its stars are now scattered in an area 100 times larger than the original galaxy!" Said Ortwin Gerhard , leader of the dynamic group at the Max Planck Institute for Extraterrestrial Physics. The July 2018 observations with ESO's very large telescope revealed that the giant elliptical galaxy had swallowed the entire medium-sized galaxy over the last billion years.
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The M87, reproduced above by NASA's Spitzer Space Telescope, houses the supermassive black hole that projects two streams of material in space at a speed close to that of light. The inset shows a close-up view of the shock waves created by the two jets. This image of NASA's Spitzer Space Telescope shows the entire M87 galaxy in infrared light.
Located about 55 million light-years from Earth, the M87 has been the subject of astronomical studies for over 100 years and has been photographed by many observatories of NASA, including the telescope Hubble Space, the Chandra X-ray Observatory and NuSTAR.
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In 1918, the astronomer Heber Curtis noticed for the first time "a curious right ray" extending from the center of the galaxy. This shiny stream of high energy material, produced by a disc of material rapidly rotating around the black hole, is visible under several wavelengths of light, radio waves to X-rays. When the particles in the jet touch the interstellar medium (the scattered material filling the space between the stars in M87), they create a shock wave that radiates in the lengths of infrared and radio light, but not in visible light. In the Spitzer image, the shock wave is more important than the jet itself.
The above zoom video begins with a view of the ALMA telescope network in Chile and focuses on the heart of the M87. It presents successively more detailed observations and results in the first direct visual evidence of the silhouette of a supermassive black hole. (ESO / L. Calçada, Digitized Sky 2 Survey, ESA / Hubble, Astron Radio, De Gasperin et al., Kim et al., EHT Collaboration).
On the right, the very first image of the black hole at the heart of the M87 galaxy, taken by the Event Horizon telescope. The wide-field view of NASA's Chandra X-ray observatory on the M87 galaxy (left) reveals the jet of high energy particles thrown by intense gravitational and magnetic fields around the black hole. Credit: X-rays (left): NASA / CXC / Villanova University / J. Neilsen; Radio (right): Event Horizon Telescope Collaboration.
Peter L. Galison, professor of history of science at Harvard, collaborator of the Horizon Event Telescope (EHT), said the scientists had proposed theoretical arguments in favor of black holes as early as 1916. This is however that in the 1970s that researchers supported the theory by observing: extremely dense areas of matter. Scientists announced in 2016 to have detected, for the first time, gravitational waves. In the opinion of many, they had been caused by the merging of black holes and were therefore proof of their existence.
This image marks the culmination of years of work by a team of 200 scientists from 59 institutes in 18 countries. The project, which also included scientists from the Harvard Black Hole Institute, is based on data collected from eight telescopes between Hawaii and the South Pole.
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Unlike the monster of the M87, 1500 times more massive than the central black hole of the Milky Way, Sag A * has four million times the mass of our sun, about 44 million kilometers wide. It may seem like a big target, but for the Earth's telescope network some 26,000 light-years away (or 245 trillion miles), it's like trying to photograph a golf ball on the moon.
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"More than 50 years ago, scientists found that there was something very bright at the center of our galaxy," said Paul McNamara, astrophysicist at the European Space Agency and expert of the holes blacks, Marlowe Hood from AFP. Its gravitational attraction is powerful enough for stars to revolve around it very quickly – as fast as 20 years earlier than the journey of our solar system, which takes about 230 million years to circle the center of the Milky Way .
"We are sitting in the plain of our galaxy. You have to look through all the stars and dust to get to the center, "said McNamara.
The Daily Galaxy via EHT, The Guardian,
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