Black holes are regions of space where the gravitational pull is so strong that nothing can escape.
Paris, France:
An international team of astronomers on Thursday unveiled the first image of a supermassive black hole at the center of our Milky Way galaxy – a cosmic body known as Sagittarius A*.
The image – produced by a global team of scientists known as the Event Horizon Telescope (EHT) Collaboration – is the first, direct visual confirmation of the presence of this invisible object, and comes three years after the first image of a dark distant galaxy. hole from
“It is very exciting to show you this best image of Sagittarius A* today,” EHT project director Huib van Langvelde said at a press conference in Garching, Germany.
Black holes are regions of space where the gravitational pull is so strong that nothing, including light, can escape.
Thus the image does not depict the black hole itself, as it is completely dark, but rather the glowing gas that surrounds the event – which is four million times more massive than our Sun – in a luminous ring of bending light. .
“These unprecedented observations have greatly improved our understanding of what happens at the center of our galaxy,” said Geoffrey Bower, EHT project scientist at Academia Sinica in Taiwan.
Bower also said in a statement by the French National Center for Scientific Research (CNRS) that the observations had “provided new insights into how these massive black holes interact with their surroundings”.
The results have been published in The Astrophysical Journal Letters.
– virtual telescope –
Sagittarius A* – abbreviated to SGR A*, pronounced “Sad-a-Star” – owes its name to its location in the direction of the constellation Sagittarius.
It has been assumed to exist since 1974, with the detection of an unusual radio source at the center of the Milky Way.
In the 1990s, astronomers mapped the orbits of the brightest stars near the center of the Milky Way, confirming the presence of a supermassive compact object there – work that led to the 2020 Nobel Prize in Physics.
Although the presence of a black hole was thought to be the only plausible explanation, the new image provides the first direct visual evidence.
Since it is 27,000 light-years away from Earth, it appears in the sky to be the size of a doughnut on the Moon.
Capturing images of such a distant object requires building an “Earth-sized” virtual telescope called the EHT to link eight giant radio observatories across the planet.
These include the Institute for Millimeter Radio Astronomy (IRAM) 30-meter telescope in Spain, the most sensitive single antenna in the EHT network.
EHT observed Sgr A* continuously for several hours to several nights – a similar idea to long-exposure photography and the same process used to produce the first image of a black hole released in 2019.
That black hole is called M87* because it is in the Messier 87 galaxy.
– moving target –
The two black holes have surprising similarities, despite the fact that Sgr A* is 2,000 times smaller than M87*.
“Close to the edge of these black holes, they look surprisingly similar,” said Sera Markoff, co-chair of the EHT Science Council and Professor at the University of Amsterdam.
Both behaved as predicted by Einstein’s 1915 theory of general relativity, which holds that the force of gravity arises from the curvature of space and time, and that cosmic objects change this geometry.
Despite the fact that SGR A* is very close to us, imaging presented unique challenges.
The gas surrounding both black holes moves at the same speed, close to the speed of light. But while it took several days and weeks to orbit the larger M87*, it completed the orbit of Sgr A* in a matter of minutes.
The brightness and pattern of the gas around SGR A* changed rapidly as the team observed it, said EHT scientist Chi-Kwan Chan of the University of Arizona, “little bit trying to get a clear picture of a puppy chasing its tail.” like”. ,
Moving targets required researchers to develop complex new tools.
The resulting image – the work of more than 300 researchers in 80 countries over a period of five years – is the average of several images that reveal the invisible monster lurking at the center of the galaxy.
Scientists are now eager to compare the two black holes to test theories about how the gases around them behave – a phenomenon poorly understood to play a role in the formation of new stars and galaxies.
The investigation of black holes – particularly their infinitely small and dense centers known as singularities, where Einstein’s equations break down – has helped physicists deepen their understanding of gravity and develop a more advanced theory. can help.
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