Our first photo of a black hole was a great moment for science. But we can not stop there. We need better photos that deliver more information. This is how we will learn even more about these strange giants who break the rules.
Now, a group of astronomers from Radboud University in the city of Nijmegen, the Netherlands, together with the European Space Agency and other partners, are developing a plan to obtain much sharper images of black holes.
The first image of Event Black Telescope (EHT) of a black hole was a scientific triumph and a feat of cooperation, engineering and technology. Also include the innate curiosity of our nature about nature. It is a powerful and effective mixture.
But, the image was a bit blurry, right? It's still a triumph, and many new research and articles will emerge from it. But could it be even better?
The group of scientists has a plan to launch radio telescopes into space to obtain clearer images of black holes. They have published an article in the journal Astronomy and Astrophysics detailing their plans. Your ultimate goal? To test Einstein's Theory of General Relativity, again.
The EHT is a group of radio telescopes around the world that operate together. They work on the principle of interferometry. Together, the "domains" act as a kind of virtual telescope the size of Earth. This is how we have a telescope big enough to see a black hole. But the EHT is hampered by the same as other terrestrial telescopes: the Earth's atmosphere.
The atmosphere of the Earth can create many problems for astronomers. The telescopes have to adapt in some way to the atmosphere to gather images of objects at great distances. That's why telescopes are built in special locations: ideally in high-altitude arid environments.
EHT radio telescopes are located in high altitude locations around the world. They are in the Alps, in the Sierra Nevada, in Atacama and in Hawaii. But they are still limited by the atmosphere of the Earth. And that atmosphere prevents the most frequent radio waves from reaching the areas.
There is another limiting factor for the effectiveness of the EHT: the size of the Earth. On Earth we can only use interferometry to link the areas no further apart than the "width" of the Earth. Therefore, any virtual telescope is limited by the size of our planet.
The authors of the article have a solution for both the problem of the atmosphere and the problem of the size of the Earth. Put the radio telescopes in place.
They call their proposed project the Event Horizon Imager (EHI), and say that it can produce images of black holes five times sharper than the EHT. The idea is to put two or three satellites in orbit that act as radio observatories. Over there, they would be free of the two limitations of the EHT.
"There are many advantages in the use of satellites instead of permanent radio telescopes on Earth, as in the case of the Horizon Event Telescope (EHT)," says Freek Roelofs, a PhD candidate at Radboud University. and main author of the article. "In space, you can make observations at higher radio frequencies, because the frequencies of the Earth are filtered by the atmosphere. The distances between telescopes in space are also greater. This allows us to take a big step forward. We could take images with a resolution more than five times what is possible with the EHT. "
The team created simulated images of black holes that represent what the EHI could see.
The sharper images of a black hole will lead to better information that could be used to test Einstein's Theory of General Relativity in more detail. "The fact that satellites move around the Earth offers considerable advantages," says radio astronomy professor Heino Falcke. "With them, you can take almost perfect images to see the real details of black holes. If small deviations from Einstein's theory occur, we should be able to see them. "
Other tests of Einstein's Theory of General Relativity are one of the main objectives of the EHI. In an email exchange with Universe Today, lead author Freek Roelofs explained it this way: "Einstein's theory of general relativity predicts exactly what size and shape a black hole shadow must have. Alternative theories of gravity predict different sizes and shapes, but the difference with the prediction of general relativity is generally smaller than about 10%. So, in order to distinguish between general relativity and other theories of gravity, we need the high-resolution images that we can only get from space-based observations. "
Yes, there are other theories of gravity. Although every time scientists can test Einstein's TGR, the evidence supports the theory, there are still some disturbing questions. There are multiple alternative theories of gravity in the world of science, and they are mostly related to our unanswered questions about black holes, dark matter, and dark energy.
There are dozens of alternative theories of gravity, and most of them have not had good results against the evidence. But they exist because if one of these experiments designed to test Einstein's TGR proves to be false, we must have another theory to work with.
There are many challenges to be solved if the EHI comes to pbad. With the EHT, each observatory stores its data on a hard disk that is delivered to a data processing center. All the data of each scope are combined using an atomic clock for extreme precision. But how will that work in space?
"With the EHT, the hard drives with data are transported to the processing center by plane. Of course, that is not possible in space, "said Volodymyr Kudriashov, a researcher at the Radboud Radio Lab who also works at ESA / ESTEC, said a laser link could be used to send the data to Earth for processing. There is already a precedent for that, they say, and future planned space missions will refine laser communications even more.
Another challenge is the precise position and speed of the satellites needed to produce clear images. "The concept requires that you can determine the position and speed of satellites very accurately," Kudriashov said. "But we really believe that the project is feasible."
The EHI would work in conjunction with the EHT as a type of hybrid interferometer, combining the data from all terrestrial observatories with data from orbital observatories. The best of both worlds.
"The use of such a hybrid could provide the possibility of creating moving images of a black hole, and could observe even more and also weaker sources," said Falcke.