Black holes are one of Einstein’s most profound predictions of general relativity. Originally studied as a mere mathematical consequence of the theory rather than as related physical objects, they were soon regarded as the general and sometimes inevitable result of gravitational collapse. originally formed a galaxy.
In fact, most physicists suspect that our galaxy revolves around a supermassive black hole at its center. There are other ideas too – 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 led by me from the University of Central Lancashire, revealed the first image of the object lurking at the center of the Milky Way – and it’s a supermassive black hole.
This means that there is now a lot of evidence for a black hole, named Sagittarius A*. While it may seem a bit intimidating to be near such a monster, it is in fact 26,000 light-years away, which is reassuring. In fact, since the black hole is so far away from Earth, to us it’s about the same size in the sky as a donut would be on the Moon. Sagittarius A* also seems rather inactive – it doesn’t gobble up a lot of material from its surroundings.
Our team is part of the global Event Horizon Telescope (EHT) Collaboration, which used observations from a worldwide network of eight radio telescopes on our planet – form a single virtual telescope the size of Earth – for stunning images. Breakthrough after the 2019 release of the collaboration first image of a black holecalled M87*, at the further center Messier Galaxy 87.
Looking into the dark
The team observed Sagittarius A* for several nights, collecting data for several hours in a row, similar to using a long exposure time on a camera. Although we can’t see the black hole itself, because it’s completely dark, the glowing gas around it shows an amazing signature: a dark central region (known as the “dark”) surrounded surrounded by a ring-like structure. The new view captures light being bent by the powerful gravity of the black hole, which is 4 million times the mass of our Sun. The discovery also offers valuable clues about the activity of black holes, which are thought to be at the center of most galaxies.
What’s surprising about this image is that it looks very similar to the image of the M87* that we published three years ago – which certainly comes as a surprise. The reason for the similarity is that while the black hole M87* is about 1,000 times larger, the Sagittarius black hole is about 100 times closer. Both obey Einstein’s general theory of relativity, which shows that Einstein was right by a factor of 1,000 on the size scale. For a physicist, this is very important. The theory of relativity has been around for a century and it is still being proven correct. I think even Einstein himself might be surprised by that!
The publication of this photograph of the A* Sagittarius black hole is an extremely exciting achievement of the partnership. When I first saw the image, I thought: this tells us a lot. I can’t wait to start writing about it and interpreting the picture. We had a lot of meetings to come to an agreement on what it told us. To begin with, we met face-to-face in different parts of the world. Then COVID happened and suddenly nobody could go anywhere. So online meetings have become the norm, as in every other aspect of life. This definitely slows us down.
My role is to help write two of the six papers was published in the Astrophysical Journal Letters: the first, an introduction to observations; and the third, where we discuss how we make a picture from observations, and how reliable that picture is.
In addition, I am a “contributing author” on all six articles. This is an administrative role in which I handle all correspondence between our team of more than 300 astronomers and the academic journal that publishes our findings. This has its challenges, as I have to deal with every typo and every typographical error.
I also had to channel comments from my colleagues. Since the majority of the collaborators worked in the US or East Asia, that meant they worked through the night UK time. As a result, every morning I go to work to find about 100 overnight emails from colleagues – a rough start to any day.
Anyway, we finally got there – and the brilliant results were worth all the work.
Public statement: Derek Ward-Thompson does not work for, consults with, owns shares in, or receives funding from any company or entity that may benefit from this article and does not disclose any affiliates that may benefit from this article. related beyond their academic appointment.
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