“This is a great job”: scientists saw a hole in the center of our galaxy

The Event Horizon Telescope was able to take a microwave image of the central object of the Milky Way – a supermassive black hole 26,000 light-years from Earth in the constellation Sagittarius – Sagittarius A*. This study is presented in six articles published in the journal. Astrophysical Journal Letters.

About new results with the most powerful tool in a private test press conferences Astronomers from the European Southern Observatory (ESO) and the EHT project were announced at the ESO headquarters in Munich. ESO is an international organization uniting more than ten states and operating powerful telescopes observing the sky in the southern hemisphere, especially Chile. The Event Horizon Telescope project is a joint global network of radio telescopes that allows observing the neighbors of especially supermassive black holes with unprecedented resolution.

In 2019, this project imaged a supermassive black hole at the center of one of its neighboring galaxies, M87*.

It looked like a fuzzy black circle wrapped in a fiery orange ring, which has been compared to the Eye of Sauron in the Lord of the Rings series. The observed round shadow of a black hole served as additional confirmation of Einstein’s General Theory of Relativity (GR), which predicted an exactly round shadow.

“For the first observations, it was important to choose an object bright and close enough to see the precious “shadow.” million light-years) is one of the supermassive black holes,” explains Alexei Rudnitsky, Vice-President of the FIAN Astrospace Center.

Now, the EHT collaboration has released the first Sgr A* image, averaged over thousands of images generated using various computational methods – and they all correspond exactly to the EHT data. This generalized image preserves the most frequently observed features in different images and suppresses rarely visible features. Along with the previous image of M87*, this is the most carefully calibrated interferometric image ever taken by the researchers.

The smaller mass of the Milky Way black hole, and thus the smaller dynamic scale of Sgr A*, made the visualization and analysis of the EHT data much more difficult.

The data analysis process used black hole simulations run by supercomputers in different parts of the world. Comparing the resulting image with the models shows that Sgr A* is indeed spinning, and earthly observers are looking at it from the side, not from above. The diameter of the event horizon of this black hole – that is, the limit where the second cosmic velocity exceeds the speed of light – is 25.4 million km. The mass of this black hole is about 4.3 million times the mass of the Sun, which is quite small by the standards of such objects – black holes at the centers of other galaxies often reach billions of solar masses.

“We can’t say we discovered anything unexpected and extraordinary, but this is a technically important result. It was extraordinarily difficult to get an image of this black hole due to the need to create new data processing algorithms, and within a few years people were coping with it. It’s a great work, probably in demand in radio interferometry.” will see, these algorithms will be used in a number of other observations.We got a good example of everything working and everything great, astrophysicist Sergei Popov, a lead researcher at SAI MGU, told socialbites.ca.

– The general theory of relativity is working, algorithms are working, telescopes are working, and astronomers say there will be even better pictures in a year. These are the first steps to get much higher quality images that can be used for general relativity checks and other interesting things.”

Of particular interest in this context is that EHT was able to distinguish some structural features of the Sagittarius A* object. Sgr A* image shows the same ring structure and shadow as black hole M87*. The observed ring is the result of gravitational lensing with a diameter accurately predicted by general relativity using only the mass and the distance from the black hole. Coincidentally, the observed angular diameter of Sgr A* is only marginally different from that of M87*, which is 1500 times larger and 2000 times further away.

“We see that the black hole at the center of our Galaxy has a photon ring, and this is the second image of such a ring in history. This is not a photograph of the disk, the black field inside is not an image of the black hole itself, but about one and a half times its size. “They have improved upon the previously made mass estimate. Now the mass is not measured in a thousandth of a parsec, but in a Schwarzschild radius and a half,” says Popov.

The data itself was obtained by the Global Telescope Facility in April 2017 and analyzed by an international research team of more than 300 people. After this stage, EHT continued its work and gradually expanded its capabilities by adding new stations, increasing bandwidth and introducing higher frequencies. Current and new observations with EHT Sgr A* and M87*, combined with innovations in analysis and theoretical modeling, will contribute to new discoveries in black hole physics.