We cannot observe black holes directly, only through the effects they create, for example, if they have a companion from whom material is taken away. However, it is assumed that our galaxy may be full of small, mostly lonely, so it can only be seen in special cases with black holes. THE Website review of the Hubble Space Telescope it resembles the density of a black hole as if a navy were being compressed into a basketball. A lone black hole is usually an object with multiple solar masses, whose strong gravity curves the space around it, and the path of starlight also deviates as a result of this effect, allowing them to be detected.
Astronomers say hundreds of millions of such black holes could make their way through the hundreds of billions of stars in our galaxy, but detecting them is an amazing challenge. Recently, however, it may have succeeded, thanks to the fact that the light of a star passing behind the supposed black hole has been amplified and deflected for a short time by gravity. Researchers have been able to detect this through long-term observational and measurement work, thanks to Hubble’s excellent resolution. The black hole typically deflected the star’s light, which precludes other objects with excellent gravitational lens effects.
For the first time, with a series of observations lasting about 6 years, we were able to directly prove that a lone black hole is migrating through our galaxy, interstellar space, by measuring the mass of an invisible object. So far, we’ve only come across such small black holes with a few star weights through companion stars, so the real special thing now is.
Using the method of gravitational microlensing, the change in the light of the star behind the black hole showed the presence and nature of the black hole. Source: NASA, ESA, STScI, Joseph Olmsted –
The black hole now discovered is in the arms of Carina-Sagittarius of the Milky Way, about 5,000 light-years away, but the discovery statistically means that the nearest may be only 80 light-years away (our nearest star neighbor, Proxima Centauri, is 4 light-years away). Similar solitary black holes are formed from giant stars that weigh approx. 20 solar masses, After completing their constellation in a supernova explosion, their remains are compressed to an extremely dense due to their own gravity. Because the explosion is not completely symmetrical, the resulting black hole will set off in the galaxy to gain momentum. Circled is the star that brightened during the observation period due to the putative black hole. Source: STScI / NASA / ESA –
Many terrestrial telescopes monitor the star-rich central region of the Milky Way for signs of a black hole and then use Hubble to carry out follow-up investigations to confirm – or refute – the hypothesis. Currently, the stray was found using this method, STScI, which also operates Hubble, and a team of researchers from the University of Berkeley were investigating one of the possible sites, and although there are small differences in their results, both teams found a stray black hole. has been identified. 2011-2017, a star shining and fading on a Hubble shot due to an alleged black hole, Forrás: NASA, ESA, Kailash Sahu(STScI), with image processing by STScI’s Joseph DePasquale –
The method of gravitational microlensing is as follows: a distant object, e.g. we try to observe an exoplanet by waiting for another object of greater mass to pass between the target and the Earth. The gravity of a massive intermediate object deflects and amplifies the light of a farther target object, thus making the invisible visible. Now, however, astronomers were not interested in the object behind, but in the one that triggered the lens effect. Among the approximately 30,000 microlensed cases examined so far, the black hole has a very unique fingerprint. The very strong gravity of the black hole stretches the light of the star for more than 200 days, and the possibility that the color of the star has not changed – another star would change it, the light of the two stars in front of each other – now however, this did not happen. In our case, the elongated light of the star in the background could be detected for 270 days. With the help of Hubble, the mass and motion of the black hole could also be determined by making precise measurements of how much the black light was emitted by the black hole. One research group says it has 7 solar masses, which is clearly in the range of the black hole, the other research group says it has 1.6-4.4 solar masses, in which case the larger mass means a black hole and the smaller mass means a neutron star. The speed of the black hole was given by researchers at 160,000 kilometers per hour, which is faster than other stars in that region of our galaxy (roughly equivalent to getting to the moon in 3 hours). Whether the object is a black hole or a neutron star, it is definitely the first sight to detect a lonely, dark, star-sized object with this method. – 
