A “groundbreaking” discovery on the Milky Way will be announced on May 12: what you need to know

On Thursday 12 May, there will be a “revolutionary” announcement about the Milky Way. The image of Sagittarius A *, the giant black hole at the center of the galaxy, is hypothetical.

Kl. 15.00 Italian time (13.00 GMT) on Thursday 12 May, the announcement of a groundbreaking discovery concerning the Milky Way, our galaxy, is expected. Six joint press conferences are planned from Mexico City, Munich, Tokyo, Santiago de Chile, Washington DC and Taipei to disseminate scientific information, a likely step for our knowledge. Since the same team from the International Event Horizon Telescope (EHT) project that published the first image of a black hole in April 2019 is involved, there is every reason to believe that the “photograph” of Sagittarius A *, the supermassive black hole, could spread. at the center of our galaxy.

This would be an absolutely extraordinary result for several reasons. Sagittarius A * actually has very different properties compared to the “heart of darkness” presented in 2019, the supermassive black hole at the center of the M87 galaxy, immortalized thanks to the synergistic work of eight sophisticated radio telescopes scattered around the globe. : Alfonso Serrano large millimeter telescope; Atacama Large Millimeter Array (ALMA); The James Clerk Maxwell Telescope; South Pole Telescope; the submillimeter array, the submillimeter telescope; IRAM and APEX. M87 is 50 million light-years from Earth, but it is a colossal object with a mass equivalent to 6.5 billion suns and can be easily pointed out into deep space. Sagittarius A *, although much closer (26,000 light-years), has a mass of about 4.3 million suns and a diameter of “only” 44 million kilometers. Moreover, it is an object largely hidden by clouds of interstellar dust and gas that are at the center of the galaxy, so it is much less easy to put in the viewfinder than the M87.

Because of the distances and dimensions involved, getting a picture of Sagittarius A * would be like photographing a bee on a flower about 5,000 miles away, or roughly the distance between Lisbon and New York. There is no instrument on Earth with such a resolution, yet the scientists from the Event Horizon Telescope (EHT) rely on a network of radio telescopes that work in synergy thanks to a process called interferometry, simulating a giant Earth-sized instrument. It was thanks to this approach that three years ago they managed to get the picture of the M87; it is now believed that they were also able to capture the intangible details of Sagittarius A *. A press release from the European Southern Observatory (ESO) confirmed that “important audiovisual support material” will be released during the press conference, while an ad hoc press release will be issued 7 minutes after the start of the press conference, which will be opened on the basis of words from the Director-General of ESO.

The black hole in the middle of the M87. Credit: EHT

Remember that “photographing” a black hole is an extremely complex task. They are, in fact, completely invisible objects; the only thing we can see is the event horizon, the boundary of the black hole, beyond which not even light can escape from the destructive gravity. That’s why the first picture of M87 looks like a weird donut. A similar picture is also expected for Sagittarius A *. Black holes can be detected by gravitational interaction on nearby objects, such as when they consume matter from a star in a binary system. It is believed that there is a supermassive black hole in the center of each galaxy, much larger than the black holes with star mass, which are formed after the stars’ ‘death’. It is only left to wait for the press conference on May 12 to learn about the revolutionary discovery on the Milky Way.

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