Radiophysics have found a way to "photograph" a black hole

The first step is to study the object Sagittarius A * (4.31 million solar masses, presumably a black hole) in the center of our galaxy

Researchers from the laboratory of computer science and artificial intelligence of the Massachusetts Institute of Technology, Harvard-Smithsonian Center for Astrophysics and the Haystack Observatory have developed a new algorithm that will help for the first time in history to get a real picture of a black hole. More precisely, the area of ​​space-time, in the center of which is the black hole itself, invisible by definition.



Of course, the Internet is full of pictures of black holes, and in science fiction films and TV shows we have seen black holes hundreds of times. But all this is the fruit of the imagination of artists, designers and the scientists themselves, who only suggest what the environment of the event horizon may look like.

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If the calculations of American radio physicists are correct, and if their efforts are supported by colleagues from other countries, then we will soon find out the truth.



“The black hole is very, very far away, and it’s a very compact object,” explains Katie Bouman, lead author of research work and a graduate student at the Massachusetts Institute of Technology. “[To photograph a black hole in the center of the Milky Way galaxy] is like shooting a grapefruit on the surface of the moon, but only with a radio telescope.”



The black hole in the center of our galaxy is at a distance of 26,000 light years, it is surrounded by a radio-emitting gas cloud about 1.8 parsec in diameter. At the same time, the diameter of the black hole is estimated at only 44 million km, which is comparable with the radius of the orbit of Mercury, the closest planet to the Sun of the solar system. To detect such a distant and tiny object, a telescope with a diameter of 10,000 kilometers is required. It is very difficult to build it, because the Earth has a diameter of only 12,742 km.



Since building a telescope the size of Earth is not an option, I had to find another solution. Scientists have developed an algorithm that combines data from radio telescopes across the planet into a single whole in order to filter out noise and build a synthesized image. The project was named Event Horizon Telescope : Telescope event horizon.



“There are many advantages to radio waves,” says Bowman. “As radio emission penetrates walls, it passes through clouds of galactic dust.” We would never be able to see the center of our galaxy in the visible range, because there is too much between us. ”





^{The location of the solar system (in the center of the yellow point) relative to the center of the galaxy, where the supermassive black hole is located}



However, the advantages of radio telescopes imply their disadvantages. Because of the need to record very long waves, the size of the antenna must be gigantic. Now the largest radio telescope with one antenna on Earth has an antenna diameter of 304 meters. Therefore, for practical purposes, astrophysicists use radiointerferometers , a tool for radio astronomy observations with high angular resolution, which consists of at least two antennas spaced apart and interconnected by a cable link.



Principle of operation

If you take two antennas located at a distance d (base) from each other, then the signal from the source to one of them will come a little earlier than before the other. If the signals from two antennas are then interfered, then the source information can be recovered from the resulting signal using a special mathematical reduction procedure with effective resolution . Such a reduction procedure is called aperture synthesis .

In fact, the telescope of the event horizon is such a giant radio interferometer.



Bowman and his colleagues have already secured the support of six observatories in different parts of the world who have agreed to participate in the Event Horizon Telescope project. Confirmation of participation from other observatories is expected in the coming weeks.



According to the plan, first, the radio interferometer will be tested at Sagittarius A , a complex radio source located in the center of our galaxy. It consists of the remains of a supernova (Sagittarius A East), a complex of three gas and dust clouds (Sagittarius A West) and the most interesting - Sagittarius A * , presumably a supermassive black hole. It radiates in the infrared, X-ray and other ranges.



Data from this object will be filtered from noise and used to generate a synthetic image of a black hole and the surrounding space.



The algorithm developed by radiophysics for synthesizing data from radio telescopes into one image is called CHIRP (Continuous High-Resolution Image Reconstruction using Patch priors). After training on Sagittarius A *, it is supposed to be used to observe other large and small black holes in different regions of our galaxy, as well as beyond its borders.



Today, black holes are recorded by observatories by computer scanning, which records bright flashes of light, for example, when it absorbs a star from which a black hole “sucks” plasma.







The obtained coordinates will be used to direct the Event Horizon Telescope radio interferometer and to learn the CHIRP algorithm using the methods currently used in machine vision algorithms. Over time, the program will be able to independently detect such patterns.



The scientific work of the group of researchers at the Massachusetts Institute of Technology, the Harvard-Smithsonian Center for Astrophysics and the Haystack Observatory with details of the algorithm developed will be presented on June 27, 2016 at the Conference on Computer Vision and Pattern Recognition in Las Vegas. After that, other scientists will have the opportunity to check the calculations of their American colleagues and, if everything is correct, then we will receive the first image of the black hole in about a year.







Look forward to.