Astronomers have shown the first image of a black hole at the center of our galaxy

Scientists have presented the first image of a supermassive black hole at the center of our galaxy. The discovery was reported by the European Southern Observatory (ESO) and participants in the project called Event Horizon Telescope (EHT). The Poles also participate in the discovery.

The black hole is the area where the force of gravity is so powerful that it does not allow any matter to escape, not even light. To produce it, it is necessary to accumulate a very large mass in a small volume. The mathematical boundary of this area is called the event horizon. There are two main types of black holes: stellar masses and supermassive black holes with masses of millions or even billions of solar masses.

Scientists have long suspected that there is a supermassive black hole at the center of our galaxy. The strongest evidence so far has been observations of the motion of stars near the center (Sagittarius A*, abbreviated as Sgr A*), indicating the presence of a mass four million times greater than that of the Sun at this place.

The image presented is the first direct (visual) confirmation of the existence of this black hole at the center of the Milky Way. You can see above the shadow of the black hole and a bright ring right next to the black hole’s event horizon. The size of the black hole’s shadow is about 52 microarcseconds in the sky.

The image of the black hole was obtained as a result of the analysis of data from radio observatories cooperating in the project called Event Horizon Telescope (EHT). The scientists today presented the results of their work at press conferences held simultaneously in several locations around the world.

We’re amazed at how closely the size of the ring matches Einstein’s predictions of general relativity. These unprecedented observations have greatly improved our understanding of what is happening at the very center of our galaxy and provide new insight into how the giant black hole interacts with its environment. – underlined Geoffrey Bower from the Institute of Astronomy and Astrophysics, Academia Sinica in Taipei (Taiwan), working in the EHT project team.

The image shown is not the very first image of a black hole. In 2019, observations of black hole shadows of Messier 87 (object M87*) were announced. Both are supermassive black holes, but there are differences: M87* is about 1,600 times more massive than Sgr A*.

In the case of black holes, mass is directly proportional to radius, so M87* is also 1,600 times larger at the same time. However, due to the difference in distance, they both have a similar angular size in the sky for us. The M87* black hole is 55 million light-years away and Sgr A* is 27,000 light-years away.

Scientists point out that despite these differences, the installations are very similar. As Sera Markoff of the University of Amsterdam in the Netherlands, co-chair of the EHT Scientific Council, explains, we have two completely different types of galaxies and two completely different masses of black holes – but near the edges of these black holes they look eerily similar, which tells us that general relativity rules these objects up close, and any differences we see further out must be due to differences in the matter surrounding the holes black.

Observations of “our” black hole were much more difficult than those of galaxy M87, due to the much faster variability in the vicinity of the black hole. In both cases, the gas near the black hole is moving at the same speed, close to the speed of light. However, it takes days or even weeks to orbit M87*, whereas it only takes gas a few minutes to orbit Sgr A*. This means that the luminosity and gas structures around Sgr A* change much faster, making it difficult to obtain a stable image. Scientists had to develop methods that take gas movements into account. This is why results for M87* were announced a few years ago, and only now for Sgr A*.

A team of more than 300 scientists from 80 institutes around the world participated in the work. Several radio telescopes were used for the observations carried out in April 2017: Atacama Large Millimeter/submillimeter Array (ALMA), Atacama Pathfinder EXperiment (APEX), IRAM 30-meter Telescope, James Clerk Maxwell Telescope (JCMT), Large Millimeter Telescope Alfonso Serrano ( LMT), Submillimeter Array (SMA), Arizona Submillimeter Telescope (SMT), South Pole Telescope (SPT). Since then, the Greenland Telescope (GLT), Northern Extended Millimeter Array (NOEMA), and the UArizona 12-meter Telescope on Kitt Peak have also been added to the EHT array.

The research was published in a series of articles in a special issue of the scientific journal The Astrophysical Journal Letters.

The European contribution to this important discovery, in addition to research teams and telescopes, was also the supercomputer for EHT data fusion, maintained at the Max Planck Institute for Radio Astronomy in Germany, and financial grants from the European Council of the research and the Max Planck Society in Germany.

There are two poles in the EHT team: teacher. Monika Mościbrodzka from Radboud University Nijmegen (Netherlands) and Dr. Maciek Wielgus from the Max Planck Institute for Radio Astronomy in Bonn (Germany). Teacher. Mościbrodzka made a significant contribution to the theory related to publications, and Dr. Wielgus – to data processing. He is the first author of one of the publications on Sgr A* light curves.

Thanks to the fact that scientists now have images of two supermassive black holes (one at the top and the other at the bottom of the mass range of such objects), they can study the differences between them and better test the behavior of gravity in such extreme environments.

There are also chances of getting even better data, as the EHT observing campaign conducted in March 2022 included more telescopes than before.

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