Scientists have confirmed the existence of the black hole at the heart of the "Milky Way"

Observation of a star strengthened the assumption: there is a black hole in the center of the "Milky Way" * One of the scientists - Dr. Tal Alexander from the Weizmann Institute. The scientists tracked a star orbiting the black hole

The star orbits an object with a mass 3.7 million times the mass of the Sun - and may be the black hole. Image: Europa Southern Observatory. Simulating the position of the black hole. Its existence would hint at the galaxy creation process

The human race may never know the north of the center of the "Milky Way" galaxy - the galaxy where Earth is located - but scientists have now managed to learn a little about what goes on there. Astronomers from Europe and Israel have recently discovered reliable findings, indicating that in the heart of the galaxy - at a distance of about 26 thousand light years from Earth - is a black hole with a mass of millions of stars.

The scientists came to the conclusion that this is a black hole after they were able to measure the orbital path of a star that passed around a huge celestial body in the center of the galaxy. A report detailing the research findings was published yesterday in the scientific journal "Nature".

A black hole is a concentration of matter with great density and enormous gravity, which pulls into it everything that is near it. Astronomers have been claiming for a long time that black holes reside at the center of galaxies. The object - which is believed to be a black hole -

Already observed before and given the nickname "Sagittarius A" it has a radius only 16 times that of the Sun, but its mass is 3.7 million times greater. However, without findings indicating the effect of the object on the motion of nearby stars, it was not possible to check whether it was a black hole or another object.

The group of astronomers - led by Dr. Rainer Schodel from the Max Planck Institute for Extraterrestrial Physics in Germany, and among its members the astrophysicist Dr. Tal Alexander from the Weizmann Institute in Rehovot - used cutting-edge technology to track the orbit of the star. The decisive measurements were made with the help of telescopes located on the surface of the earth, whose mirrors change their shape, to overcome distortions caused by the earth's atmosphere.

"This is the first time that an almost complete orbit of a star moving around the black hole has been observed," Dr. Alexander told Haaretz yesterday. "Until now, only short segments of the star's orbit have been seen - something that made it impossible to know if it is actually orbiting a black hole, or another object. This is a very important step towards ruling out all other possibilities of identifying the object as something other than a black hole. This measurement has already ruled out two alternative explanations, and this greatly strengthens the hypothesis that this is indeed a black hole."

Dr. Carl Gebhardt, an astronomer from the University of Texas who wrote a commentary article accompanying the publication of the study, also believes that it is a black guy. "These findings are the best evidence received so far that supermassive black holes are not just theoretical objects, but a solid and existing fact," Gebhardt said.

According to Dr. Alexander, it is possible that in the future more findings will be discovered that teach about the black hole. "This is just an appetizer before the real meal," he says. "There is a chance that more stars will be found there - closer to the black hole. Although the chance of a star falling into the black hole in our lifetime is very small, there is a realistic chance that we will be able to follow the beginning of its 'swallowing' process."

Today, most astronomers believe that proving the existence of a black hole can provide clues about the processes that led to the creation of the galaxy itself. "It is not realistic that we will be able to see black holes that are in other galaxies," claims Dr. Alexander, "but the hope is that by studying the black hole in our galaxy it will be possible to draw conclusions about other galaxies in the universe as well."
The original knowledge

Dr. Tal Alexander from the Weizmann Institute of Science, and scientists from the Max Planck Institute in Germany, for the first time succeeded in following the trajectory of a star that orbits an "empty point in space", which is apparently a massive black hole located at the core of our galaxy - the Milky Way. A massive black hole is a celestial body whose mass is equal to a million to a billion stars like our sun.

The star that scientists were tracking passed at a speed of 5,000 kilometers per second at the closest point to the black hole: only 17 light hours from its "event threshold". The scientists say that if the star had come a little closer to the black hole, it would have fallen and been sucked into it. The findings of this research, carried out with the European Giant Telescope stationed in Chile, are published today in the scientific journal Nature.

Dr. Alexander says that the presence of a massive black hole relatively close to us gives scientists an opportunity to learn about phenomena and processes that take place in distant galaxies in the depths of the universe, as well as to better understand the processes involved in the formation and development of galaxies.

The scientists believe that massive black holes are created when many "normal" black holes merge. A black hole is a special star, a kind of "dark sun". In fact, it is a solar remnant much larger than our sun, which exploded and "lost itself knowing" in the process of supernova. This process takes place in developed solar panels, which have exhausted all possible nuclear fusion processes, the core of which is already made of iron. At this stage, the heat of the core breaks down the iron atoms into neutrons and protons, and the star begins to rapidly shrink and collapse in on itself under the influence of its own gravity (the gravitational energy that is released, it feeds the process of disintegration of the iron atoms in the core, into protons and neutrons). The rapid contraction of the star causes it to heat up, which accelerates the nuclear fusion processes taking place in it, until the nuclear fusion explosion becomes a powerful explosion. As a result of the explosion, the sun sheds its outer layers, which contain most of the material that makes it up.

The ejected material is scattered in space in all directions, and the light of the explosion illuminates large parts of the galaxy. At the same time, the Sun's core collapses and contracts in on itself. When this process takes place in a sun whose mass is much greater than our own, it ends up creating a black hole, that is, a star whose gravity is so great that it does not allow even light rays to leave it. For this reason, the star is invisible, although the effect of its gravity on its surroundings is clearly visible. For example, the orbits of stars located near the black hole are affected by the gravity of the black hole: they appear as if they are rapidly circling an "empty" point in space. Careful monitoring of such stars - as Dr. Alexander and his German colleagues did - may indicate the presence of the black hole in the place, as well as the properties of the black hole, including its exact mass.

Despite the fact that the black hole does not emit light, the material sucked into it is compressed, heated and therefore emits a lot of radiation. "This is the most efficient engine in the universe," says Dr. Alexander, "which turns mass into energy according to Einstein's famous mass and energy equivalence formula."