As one might imagine from a massive, collapsed star in which the laws of physics seem to break down, black holes hold a special place in human culture – spurring all manner of creative science fiction, real-world physical theories ideas and creative metaphors. Yet even as we gawk at the astronomical bodies first known to theorists as “dark stars,” we still haven’t been able to imagine the impossibly massive black hole at the center. of our own galaxy, and around which the rest of the galaxy the stars revolve.
So far, that is.
Scientists from the Event Horizon Telescope Collaboration (EHT) announced Tuesday that they have coordinated eight synchronized telescopes around the world to capture an image of Sagittarius A*. Four million times more massive than our own sun, Sagittarius A* has long been theorized to be a supermassive black hole, but experts couldn’t know for sure due to the difficulties of imaging this part of the sky with high precision. . The new image shows a ring of orange and gold light that becomes particularly bright in three places. In the center, and black in color, is a slightly bean-shaped hole.
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“Although we cannot see the black hole itself, because it is completely dark, the glowing gas surrounding it reveals a telltale signature: a dark central region (called a ‘shadow’) surrounded by a bright structure in ring shape,” the astronomers explained. in a statement. One of them, EHT project scientist Geoffrey Bower of the Taipei Institute of Astronomy and Astrophysics, added in the statement that “we were amazed at how big the ring matched predictions from Einstein’s theory of general relativity.These unprecedented observations have greatly improved our understanding of what is happening at the very center of our galaxy, and offer new insights into how these giant black holes interact with their environment.
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The very first direct image of a black hole was obtained in 2019 and was the culmination of years of astrophotography and research. This black hole was the supermassive black hole at the center of the galaxy M87, which has a mass of about 6.5 billion suns and is 50 million light-years away. Sagittarius A* is only 27,000 light-years away, much closer; yet, due to its position in the night sky and relatively clear field of view, it was easier to image a distant galaxy’s black hole before seeing our own.
It must be emphasized that while we see the black hole in one sense, in another sense the very concept of “seeing” one of these objects is absurd. The term “event horizon” is more than the title of a classic 1997 sci-fi horror movie. It refers to the threshold that surrounds any black hole, through which nothing can escape. The gravitational force is so strong that anything that falls stays in the black hole forever.
This naturally includes the light itself. This is why, to “see” a black hole, what we really observe are the objects that orbit around it, sometimes very close and very fast. This includes the accretion disk, the accumulation of space debris – gas and dust – that swirls around most black holes near the event horizon, generating a faint aura of light from the heat of the collision. and movement.
“Part falls in, part just forms this disc around it and this stuff glows,” Seth Fletcher, the American Scientist Articles editor who wrote a book on EHT, recently explained. “The black hole, because of the way it warps space, time around it, because of the incredible force of gravity, it casts a shadow on this glowing matter – and so that’s what we let’s see in this picture.”
To say this is a long distance photograph would be a drastic understatement. We live in a barred spiral galaxy, or a galaxy that swirls with flapping arms and has a bar-like structure in the middle made up largely of stars. Our planet is located in one of these spiral arms, and Sagittarius A* is 27,000 light years away. This means that if we traveled at the speed of light, it would take us 27 millennia to reach Sagittarius A* from our celestial home.
The EHT research team that made this discovery published their findings in the scientific journal The Astrophysical Journal Letters. Closing the announcement of their discovery, they noted that more than 300 people from around the world have participated in this effort, and EHT has more ambitions.
“Since these observations, the EHT has continued to observe and grow its capabilities through the addition of new stations, expanded bandwidth, and the introduction of higher frequency capability,” they wrote. “Existing and new observations with the EHT of Sgr A* and M87* coupled with innovations in analysis and theoretical modeling will lead to the discovery in these unique laboratories for black hole physics.”
While black holes that weigh at least 4 times the mass of our sun are regularly created in supernova explosions of massive stars, supermassive black holes like Sagittarius A*, that weigh millions or billions of solar masses, emerge differently: either by a bizarre process of gas coalescence in the early universe; or when thousands of stellar black holes merge over billions of years; or a combination of both. Supermassive black holes have unique properties compared to their much smaller counterparts. Some scientists speculate that due to the large distance between its event horizon and its central singularity, if one were to fall into a supermassive black hole, one would not be immediately stretched to oblivion by its immense tidal forces as one would in a daily black hole of 4 to 100 solar masses. On the contrary, an observer falling into a supermassive black hole could have a few hours or more before being killed by the stretching of the tides; in this period, if they were to look back out of the black hole and towards the event horizon, they would see future events in near space occurring at a hyper-accelerated rate, as outer time would appear to be speeding up as they approach the singularity. Unfortunately, this observer will never be able to communicate this information because there is no escape.
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