black holes Einstein’s theory of general relativity is among the most profound predictions. Originally studied only as a mathematical consequence of the theory, rather than as physically relevant objects, they soon came to be regarded as the general and sometimes unavoidable consequences of the gravitational collapse that initially make up a galaxy.
In fact, most physicists have suspected that our own galaxy revolves around a supermassive black hole at its center. There are other ideas as well – such as “dark matter” (an invisible substance thought to make up most of the matter in the universe). But now an international team of astronomers, including a team I lead from the University of Central Lancashire, has unveiled the first image of the elusive object at the center of the Milky Way – and it is a supermassive black hole.
Sagittarius A*, the black hole at the center of the Milky Way. EHT Cooperation
This means that there is now overwhelming evidence for a black hole, called Sagittarius A*. While it may sound a bit scary to be so close to such an animal, it is actually about 26,000 light-years away, which is reassuringly far away. In fact, because the black hole is so far from Earth, it appears to be roughly the same size in the sky as a donut on the Moon would be. Sagittarius A* also seems inactive – it isn’t eating much of the substance from its surroundings.
Our team was part of the global Event Horizon Telescope (EHT) collaboration, which has used observations from a worldwide network of eight radio telescopes on our planet – collectively forming a single, Earth-sized virtual telescope – to take stunning images. For. The collaboration follows the 2019 release of the first image of a black hole named M87* at the center of the more distant Messier 87 galaxy.
Black Holes: Looking in the Dark
The team observed Sagittarius A* over several nights, collecting data for several hours in a row, such as using long exposure times on the camera. Although we cannot see the black hole itself, because it is completely dark, the glowing gas around it reveals the signature of a story: a dark central region (called the “shadow”) resembling a luminous ring. surrounded by the structure. The new view captures light being bent by the powerful gravity of a black hole, which is four million times more massive than our Sun. The discovery also provides valuable clues about the workings of black holes, which are believed to reside at the center of most galaxies.
The amazing thing about this image is that it looks very similar to the M87* image we published three years ago – it certainly came as a surprise. The reason for the similarity is that while the M87* black hole is about 1,000 times larger, the Sagittarius black hole is about 100 times closer. They both follow Einstein’s theory of general relativity, showing that Einstein was correct by a factor of 1,000 on the size scale. For a physicist this is important. Relativity has been around for a century and is still proving accurate. I think Einstein himself must have been surprised by this!
The publication of the image of the Sagittarius A* black hole is a tremendously exciting achievement by the collaboration. When I first saw the image, I thought: it tells us a lot. I couldn’t wait to start writing about it and interpreting the image. We had several meetings to come to a consensus on what this tells us. To begin with, we were meeting face to face in different parts of the world. Then suddenly no one could go anywhere. So like every other aspect of life, online meetings became the norm. It definitely slowed us down.
I was instrumental in writing two of the six papers released in the Astrophysical Journal Letters: first, introducing the observation; and third, in which we discuss how we formed a picture from observations, and how reliable that image is.
In addition, I was the “contributing author” for all six papers. It is an administrative role in which I handled all correspondence between our team of over 300 astronomers and the academic journal that published our findings. This had its challenges, as I had to deal with every typo and every mistake in typesetting.
I also had to channel the comments of my colleagues. Since most of the collaborators are based in the Americas or East Asia, this means that they were working at night in British times. So, every morning I would come to work to find about 100 overnight emails from coworkers—a rough start to any day.
Anyway, we got there in the end – and the dazzling result was worth all the work.
This article is originally from . was published on Conversation by Derek Ward-Thompson at the University of Central Lancashire. Read the original article here.
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