this noon, the world was able to see for the first time an image of the black hole supermassive located in the center of our galaxy, the Milky Way.
The Milky Way is a spiral galaxy that contains at least 100 billion stars. Viewed from above or below, it looks like a spinning pinwheel, with our sun located in one of the spiral arms and Sagittarius A* located in the center.
astronomers believe that Almost all galaxies, including ours, have gigantic black holes at their center, from which matter and light cannot escape, making it extremely difficult to capture images of them. Experts said gravity bends and twists light chaotically as it plunges into the chasm of superheated gas and dust that forms the black hole. The artificially colored image was released today by the international consortium that operates the Event Horizon Telescope (EHT), a collaboration of 8 synchronized radio telescopes in various parts of the world. In previous attempts, our galaxy’s black hole was too accelerated to get a good picture.
Feryal Ozel of the University of Arizona announced the new look of what he called “the gentle giant at the center of our galaxy”. The Milky Way’s black hole is called Sagittarius A (asterisk) and is located near the edge of the constellations Sagittarius and Scorpius.. Its mass is 4 million times that of the Sun. This is not the first image of a black hole. The same group distributed the first in 2019, from a galaxy 53 million light-years away. The Milky Way black hole is much closer: it is 27,000 light-years away. A light year is equivalent to 9.5 billion kilometres.
The project cost nearly $60 million, with a $28 million contribution from the US National Science Foundation.
The international collaborative project EHT (Event Horizon Telescope) is a system that created a virtual Earth-sized telescope and which detected the first supermassive black hole in 2019, in the galaxy M87, and now the one at the center of the Milky Way, Sagittarius A*.
8 coordinated telescopes were able to observe the black hole and obtain the image (AFP)
Launched in 2015, this international collaboration of 80 astronomy institutes had set itself a huge challenge because observing a black hole is, by definition, impossible, since no light can escape from it. the EHT circumvented the obstacle by detecting the cloud of very hot plasma swirling around the black hole before passing the Event Horizon, the place from which nothing can ever come out, not even light, because of the strong gravity. “The silhouette of the black hole is visible against a background of glowing gas and dust.“, explains Frédéric Geth, French scientist at the National Center for Scientific Research (CNRS) and director of the Institute of Millimetric Radio Astronomy (IRAM). Founded by the CNRS and the German Max Planck Institute in 2015, IRAM is a key player in the EHT, which imaged the M87* in 2019, and now the Sagittarius A* (Sgr A*).
But, To accomplish these feats, astronomers had to overcome several obstacles. The cloud of matter surrounding black holes is only visible in a specific range of millimeter radio waves.and to be captured requires a radio telescope, a saucer-shaped antenna similar to that used for satellite television, but much larger, as the sharpness of the instrument is highly dependent on size, due to the gigantic instances and other barriers.
Scientists have revealed the first image of the black hole at the center of our galaxy using 8 radio telescopes (Photo: Conacyt)
M87* is 55 million light-years from Earth, while Sgr A* is 27,000 light-years away. But the latter is much smaller and, seen from Earth, hides behind gigantic clouds of interstellar gas and dust. No existing radio telescope would have had sufficient resolution to distinguish their silhouettes. The scientists then resorted to the principle of interferometry, in which a network of antennas located in different parts of the planet observes the same sector of the sky at the same time. The supercomputers combine the data obtained by the different radio telescopes, which makes it possible to obtain an image as if it were obtained by a single antenna the size of the Earth.
The EHT experiment took the exercise even further by using interferometry but with an even broader base (VLBI), i.e. by forming a network of eight radio astronomy observatories stretching from Hawaii, in the Pacific, to Spain – where there is an IRAM antenna – via the United States; and from Greenland to the South Pole, via Mexico and Chile. This is a challenge, because you have to have good weather at the same time in all the places on the network and, to achieve this microsecond synchronization, each place is equipped with an atomic clock.
“When you do that on a global scale, you end up with a huge antenna that has a diameter of nearly 10,000 km,” explains Frédéric Geth. The combined and synchronized data from the 8 observatories allowed us to build the image that we observe today and which goes around the world. Einstein’s theory of general relativity has so far failed to explain what happens in a black hole on the most infinitesimal scale. The black hole is “the most extreme, chaotic and turbulent environment” there is, said German astrophysicist Heino Falcke. But thanks to the EHT, certain aspects of this fundamental theory can now be tested.