US, WASHINGTON (ORDO NEWS) — Astronomers have discovered a black hole in the star system, which can be seen with the naked eye. This is the black hole closest to the Sun from all known to science. And experts believe that this is only the tip of the iceberg: soon the list of such objects will begin to grow rapidly.
The achievement is described in a scientific article published in the journal Astronomy & Astrophysics.
Very quiet and extremely close
Specialists studied a two-star system in the constellation of the Telescope, located a thousand light-years from Earth. After analyzing the movement of the bodies, they found out that this was not a duet, but a trio: an invisible third body was involved in the orbital dance.
The researchers concluded that the system (referred to as HR 6819) consists of three companions. One of the stars forms a pair with an unknown object. This tandem makes one revolution around a common center of mass in 40 Earth days. Another luminary slowly revolves around this pair, being at a great distance from it.
When scientists calculated the mass of the “invisibility”, there was no doubt about its nature.
“An invisible object with a mass of at least four solar masses can only be a black hole,” explains co-author Thomas Rivinius from the European Southern Observatory.
Indeed, for a neutron star this is too much (their maximum mass is approximately two solar). Well, an ordinary star, even dim, would be distinguishable by a 2.2-meter telescope, with which the researchers worked.
In this way, a black hole was discovered at a record small distance from the Earth.
Why do we need such a neighborhood
A black hole discovered so close is a real gift to astronomers. It can help in studying the properties of these exotic objects, as well as fairly rare massive stars from which black holes are obtained.
The very configuration of the system (the third object revolving around a close pair) is also of interest to astronomers. Theorists believe that it is in such trios that cataclysms often occur that generate gravitational waves.
True, for this the inner pair must consist of two black holes, two neutron stars or a black hole and a neutron star. The gravity of the external body will destabilize the movement of this duet, and sooner or later the members of the couple will collide with each other. Such a collision causes a surge in gravitational waves.
Of course, HR 6819 itself does not threaten this, because the partner of the black hole is an ordinary star. But this trio can serve as a model on which astronomers will test their ideas about the design of such systems.
And the impossible is possible
Finally, discovery may be the key to yet another mystery.
Recall that at the end of November 2019, the world spread the news about the amazing LB-1 system discovered in the Milky Way. As reported, it consists of an ordinary star and a black hole weighing about 70 solar. According to modern concepts, such a massive black hole cannot be obtained from a star with a typical chemical composition for the Galaxy.
Skeptics have repeatedly criticized this scientific work, claiming that its authors made certain mistakes.
Now there is a new convincing version explaining the oddities of the LB-1. The fact is that, according to the observed characteristics, the latter is surprisingly similar to HR 6819. Experts suggest that their colleagues mistook LB-1 for a binary system of a star and a black hole, which is why they overestimated the mass of the latter. In fact, a third body may be present there, and then everything falls into place. However, this can only be verified with the help of additional observations of LB-1.
This is just the beginning.
Today, only about two dozen black holes are known in the Galaxy, although there should be many more.
The problem is that black holes are really black, and finding them is not easy. Almost all such objects in the Milky Way were found thanks to the powerful x-ray radiation that emits the substance incident on them.
But the black hole in HR 6819 (the so-called system) is a real invisibility. She is too far from her companion to steal matter from him with her gravity. Therefore, nothing falls on her. And where there is no falling matter, there is no radiation emitting the presence of a “predator”.
Experts believe that this situation is typical. That is why so few black holes are known.
But the way invisibility was discovered in HR 6819 can be applied to many star systems. This means that in the future it will be possible to open many black holes, if you look closely at the movement of famous stars in search of invisible companions.
“There must be hundreds of millions of black holes in the Galaxy, and we only know a few. Now that we know where to look, there should be more,” summarizes Rivinius.
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