Sidereal Messenger: Astronomers get an image of the black hole at the center of the Milky Way

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For the first time, astronomers have managed to capture the shadow region of the giant black hole that lives at the heart of our galaxy, the Milky Way.

The result, obtained by the international consortium EHT (Event Horizon Telescope), was presented at an event organized in Washington by the US National Science Foundation.

The name of the project, which is led by researchers at the Harvard-Smithsonian Center for Astrophysics, alludes to the mathematical boundary that separates the point of no return from a black hole. Crossed the event horizon, the object’s gravity is so great that nothing can escape it, including light. Hence the name of this class of stars, as well as its expected appearance: a dark shadow, corresponding to the region from which light can no longer escape.

The prediction of the visual appearance of a black hole came true in 2019, when the EHT team presented the first direct image of a black hole’s shadow – in this case, of the giant object that lives at the heart of the galaxy M87, at 53, 5 million light-years away, with a mass equivalent to that of 6.5 billion suns.

It was the culmination of decades-long work exploring a technique known as very long-base interferometry, which aims to combine observations made by several separate telescopes separated by long distances into a single image. This is roughly equivalent to having a telescope whose area is the size of the greatest distance between the different elements.

The first observation by the EHT team was carried out in 2006, and the data that generated the image of the giant black hole of M87 were collected from eight sets of radio telescopes, spread across Europe, the United States, Chile and even the South Pole. In practice, it was like having a telescope the size of Earth itself. And only then was it possible to detect the shadow of the object.

The original plan was always to target two objects: besides the M87 black hole, the most obvious target – the black hole at the center of our own galaxy, an object known as Sagittarius A* (pronounced “a-star” and, of course, is in the constellation Sagittarius). But he was more defiant. Although much closer, about 30,000 light-years from Earth, it is also much smaller, with a mass of 4 million suns.

In 2019, the EHT group said it had Sagittarius A* results, but more difficult to process, promising a presentation soon. The “soon” became 2022, but it arrived. Now, for the first time, we get a close-up view of the monster that lives at the heart of our galaxy.

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