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Astronomers have just managed to take the first picture of a black hole and the next challenge to take up is to take even sharper images, so as to be able to test Einstein's theory of general relativity.
Astronomers from Radboud University, as well as the European Space Agency (ESA) and others, are proposing a concept to achieve this goal by launching radio telescopes in the space. They publish their plans in the scientific journal Astronomy & Astrophysics.
The idea is to place two or three satellites in circular orbit around the Earth to observe black holes. The concept is called Event Horizon Imager (EHI). In their new study, scientists present simulations of what Sagittarius A * black hole images could look like if they were taken by satellites like these.
More than five times stronger
"There are many advantages to using satellites rather than permanent radio telescopes on Earth, such as with the Horizon Event Telescope (EHT)," says Freek Roelofs, Ph.D. candidate at Radboud University and lead author of the Ph.D. ; 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 the telescopes in the space are also larger This allows us to take a big step forward, we could take images with a resolution more than five times what is possible with ISE. "
Sharper images of a black hole will lead to better information that could be used to further test Einstein's theory of general relativity. "The fact that satellites move around the Earth has considerable advantages," says radio astronomy professor Heino Falcke. "With them you can take almost perfect pictures to see the real details of the black holes.If small deviations from the Einstein theory occur, we should be able to see them."
The EHI will also be able to image about five additional smaller black holes than those on which the EHT is currently focusing. The latter are Sagittarius A * in the center of our Milky Way and the M87 * in the center of Messier 87, a gigantic galaxy of the Virgin group.
Technological challenges
The researchers simulated what they could see with different versions of the technology under different circumstances. To do this, they used models of plasma behavior around the black hole and the resulting radiation. "The simulations look promising from a scientific point of view, but it's hard to overcome the technical difficulties," says Roelofs.
Astronomers collaborated with scientists from ESA / ESTEC to study the technical feasibility of the project. "The concept requires that you be able to accurately determine the position and speed of satellites," said Volodymyr Kudriashov, a researcher at Radboud Radio Lab, also at ESA / ESTEC. "But we really believe that the project is achievable."
It is also important to consider how satellites exchange data. "With EHT, hard drives containing data are flown to the processing center, which is obviously not possible in the space." In this concept, the satellites will exchange data via a laser link, the data being partially processed on board before being returned to Earth for further analysis. "There are already laser links in the space," notes Kudriashov.
Hybrid system
The idea is that satellites will initially work independently of EHT telescopes. However, a hybrid system is also envisaged, the orbiting telescopes being combined with those of the Earth. Falcke: "The use of a hybrid system like this could offer the possibility of creating animated images of a black hole, and you may be able to observe even more sources and more low. "
The research is part of the BlackHoleCam project, an ERC Synergy Grant awarded in 2013 to a team of European astrophysicists to visualize, measure and understand black holes. BlackHoleCam is an active partner of the Event Horizon Telescope collaboration.
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