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What will the Event Horizon Telescope’s next milestone be?

Now that the Event Horizon Telescope astronomers have released the image of the supermassive black hole in the Milky Way, they are also planning to start making videos of the two black holes they photographed. They also look for other distant black holes that are large enough to study.

On May 12, the Event Horizon Telescope (EHT) revealed the first image of the black hole at the center of the Milky Way. With that, the telescope has captured images of both that black hole, called Sagittarius A* (or Sgr A*), and M87*, the black hole at the center of the galaxy M87. The team that created the images will now focus on new milestones. What’s on the agenda?

Sagittarius A*, the black hole at the center of the Milky Way. Image: Event Horizon Telescope (EHT).

First, the researchers have yet to study many recent observations. The images of Sgr A* and M87* are both compiled from data collected in 2017. Since then, there have been two more observation periods with the EHT, adding additional telescopes to the original network of eight.

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‘In 2018 we collected data with one extra telescope, in 2022 with three extra telescopes. We’re working very, very hard to get that to you… as soon as we can, but I can’t make any promises about when,” EHT researcher Lia Medeiros of the Institute for Advanced Study in New Jersey said at a press event on May 12. . It could be years before the results of that analysis are released, she said.

light knobs

One thing that this work is expected to clarify is the structure of the material around Sgr A*. This mainly concerns the three bright ‘nodes’ of light that can be seen in the new image. Due to the way the photo was taken, those bright spots could have been formed by the technology used and not a natural phenomenon. “The knots tend to align with the directions we have more telescopes in,” EHT researcher Feryal Özel of the University of Arizona said at the press event. “Although you expect these extra bright spots naturally, we don’t trust them very much in our data yet.”

Also read: Astronomers take first picture of ‘our’ supermassive black hole: Sagittarius A*

So far, the images are in line with Albert Einstein’s general theory of relativity. Further analysis can give us insight into whether that theory is going down in the extreme regions around black holes. “That should at some point give us a clue to something other than our current formulation of gravity with general relativity,” said Özel. “But we don’t see any flaws in that theory yet.”

Movies

Finally, another key goal of the EHT team is to create videos of Sgr A* and M87* as the material around them moves and changes over time. “We’ve tried to make a movie with the data we have,” EHT researcher Katie Bouman of the California Institute of Technology said at the press event. But while her team does have some useful data, it’s not enough right now to create movies of the black holes, she said.

The additional telescopes recently added to the EHT collection should help with that. These will collect data in multiple wavelengths, so that the resolution of the images will increase and color photographs can also be taken. On the images released so far, the colors have been added later to indicate brightness.

So far, these two black holes are the only ones we know of that can be imaged by the EHT at a high enough resolution to see their silhouettes against the light of the hot plasma around them. With Sgr A* this is possible because of its proximity to Earth, with M87* because of its colossal size. The search is still underway for other supermassive black holes that the researchers could observe and compare with these two. Based on statistical studies, there should be other black holes large enough and not too far away for the EHT to decompose, but researchers haven’t found them yet.

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