Historical announcement: Release of the first image of Sagittarius A *, the huge black hole in the center of our galaxy

Substance orbiting the supermassive black hole Sagittarius A * in the center of our galaxy. The size of the ring astonished scientists with its agreement with previous estimates based on Einstein’s general theory of relativity. Image credit: EHT collaboration

The long-awaited press conference for astronomers from Event Horizon Telescope (EHT), a global network of radio telescopes established through international cooperation that began in 2009, has finally taken place, and the announcement, although many have been waiting, is a message that is likely to go into the history of astronomy. Researchers have released the first image of the supermassive black hole in the center of the Milky Way, called the Sagittarius A *.

It is the closest supermassive black hole on Earth.

Although this is the second image of a black hole ever made after the image of the black hole in the center of the M87 galaxy, published in April 2019, this is probably even more valuable for two reasons. First of all, this is our galaxy, and therefore that supermassive black hole in question is the closest to us of all that has been discovered.
Then it’s a significant announcement, because for years we’ve been told that at the center of our galaxy there is a whirlwind of materials of various kinds, including many stars, and that the gas that surrounds this area has always prevented us from to directly analyze or detect the supermassive black hole that sits in the center.

Technique called Very Long Baseline Interferometry (VLBI)

Instead, the scientists succeeded: Using a technique called Very Long Baseline Interferometry (VLBI), they used several radio telescopes to form a kind of “virtual telescope”, practically the size of Earth, the telescope with the highest resolution ever been used in astronomy.

A study launched in 2017

EHT scientists began studying Sagittarius A * and other supermassive black holes at the center of other nearby galaxies in April 2017. The same collaboration led to the aforementioned discovery of the supermassive black hole at the center of the M87 galaxy. But over time, researchers acquired more and more data about Sagittarius A * and then managed to compose a true picture, which is probably a lot more cumbersome work than that relating to the black hole in the M87.

Differences between M87 black hole and Sagittarius A *

It should be noted that the black hole in the M87 galaxy has an estimated mass of several billion times that of the Sun, while the black hole at the center of our galaxy has an estimated mass of just over 4 million times that of the Sun. . In addition to the enormous amounts of different gases and dust that surround Sagittarius A *, a factor that is and will remain a problem for future analyzes, the difference in masses is another factor that must be taken into account in relation to the severity of the investigation.

Because it was a tough business

To detect a supermassive black hole, we do not try to detect the black hole itself, which is impossible because it emits no light. We try to discover what revolves around it, which is almost always the case with supermassive black holes at the center of galaxies. One catches changes in matter and gas that swirl around the black hole as it completes a full trajectory. And if the black hole is larger, this substance takes longer to orbit the event horizon and is therefore slower and easier to detect. That’s why it took years to compose a clear picture of the black hole in the center of our galaxy: matter swirling around Sagittarius A * orbits much faster.

Astonished scientists

Geoffrey Bower, one of the EHT researchers who obtained the farm, said he was amazed that the dimensions of the ring matched data from previous predictions based on the theory of general relativity. According to scientists, these are “unprecedented observations” that will allow us to understand what is really happening at the center of our galaxy and better understand the nature of these giant black holes.

Video from the press conference

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