Black hole is a special celestial body in the universe, because it does not emit light, does not reflect light, but also absorbs light, and we observe the universe in the universe depends on light and other electromagnetic waves, so it is very difficult to see black holes, usually when the gravitational pull of the black hole has an impact on other celestial bodies, or when the black hole absorbs other celestial material to form an accretion disk, it is possible to be seen.
Black holes with accretion disks are often called quasars
Scenario simulation of the accretion disk after the black hole adsorbs stellar material
However, on February 5, a message from the Physicists Organization Network said that an international astronomical research team had discovered a "stray black hole" through the phenomenon of "microlensing", which is believed to be the first time that the astronomical community has used this method to discover a stray black hole.
Although the news was reported in recent days, the discovery was made in 2011, when the team discovered a lonely black hole roaming between the stars, and the "wanderer" formed a "microlensing lens" with a strong gravitational force, bending and twisting the light of the stars and galaxies behind it, allowing scientists to perceive its existence, and the wandering black hole is also believed to be the first such black hole to be observed.
"Microgravity lensing" effect refers to a celestial body with a strong gravitational field so that the background light behind it distorts the phenomenon, the gravitational distribution in the universe is very uneven, around the strong gravitational field celestial body, light and other electromagnetic waves will be distorted by the gravitational field, and because the periphery of the celestial body is transparent, this forms a gravitational lensing effect, the light of the background object is refracted through this lens, the shape will be bent, the position will be shifted, and the luminosity will change. Therefore, even if the celestial body that causes the gravitational lensing phenomenon cannot be seen, its presence can be felt, even if the celestial body is a black hole, which is the reason for the discovery of this "wandering black hole".
This black hole is 5153 light-years away, located within the Milky Way, has a mass about 7 times that of the Sun, and is skimming nearby stars at about 45 kilometers per second, at a speed of about 162,000 kilometers per hour. Scientists also believe that there are many similar stellar stray black holes, but because the black hole itself does not emit light, there are fewer black holes that interact with other celestial bodies, and the microgravity lensing effect is not easy to find, so stray black holes are not easy to observe, and their observation difficulty is much more difficult than that of stray stars and even stray planets.
The research team began to observe the stray black hole in 2011, but at that time, they did not notice that there was a black hole there, because it was also invisible, in fact, they have not seen what it really is, this black hole is still not even a shadow, but it can be determined that it is real through a phenomenon.
So how did you discover it? In 2011, scientists only found that the brightness of a star increased for no reason, at that time thought that it was caused by the activity of the star itself, through continuous observation and found that this was not the case, after 6 years of monitoring, they judged that only the existence of microlensing effect can occur through strange changes in the brightness and position of the star and its surrounding objects, so they thought that the light emitted by the star was bent by an invisible object in front of it (close to the direction of the observer). Because the object is invisible, it is thought to be clearly a black hole, and then judged by the strength of gravitational lensing and other factors that the mass of the black hole is about 7 suns. So while this black hole doesn't even have a shadow, its background betrays it.
Such mass black holes are generally formed by supernova explosions of massive stars, but it is also possible that massive stars directly collapsed, so they are often called stellar black holes, and the number of stellar black holes is very large, and some astronomers have deduced that there are at least 1 million to 100 million in the Milky Way.
Such a black hole is very dangerous for planets with life or civilization in the universe, because it is very difficult to observe, and its gravitational pull is super strong, if there is such a black hole near the solar system now, its existence cannot be perceived at the current level of human astronomical observation, except for the black hole that was discovered by scientists by accident and the abnormal behavior of the light and position of the background star mentioned above.
"Gravitational lensing" observation method is very different, but such a method also provides a new way for scientists to observe other black holes, especially possible black holes that are potentially dangerous to the solar system, it is necessary to observe them, although the solar system has not been affected by black holes at close range, but it does not mean that it will not be in the future, and once it appears, it is likely to cause a risk of subversive destruction to the entire solar system, so observing the existence of black holes is also a homework that humans must do. Grasping the movement of black holes is of great significance to human beings.
Resources:
"Shangguan News" February 7 article "The first black hole to float freely in the interstellar universe appeared, with a mass of about 7 times that of the sun"
Octopus from space? The new study says octopuses may have come to Earth 500 million years ago and may have been genetically altered
There is a mysterious star near the Big Dipper, which has become the first observation target of the Weber telescope, why it is it
Scientists have found that the earth has two "pawns" that have accompanied the earth for hundreds of years, or may be of great use
More dangerous than Yellowstone Volcano! The Three Sisters volcanoes in the United States are rising, and if the eruption is stronger than the Tonga volcano