For modern scientists, a black hole is one of the most mysterious phenomena in our universe. The study of such objects is difficult, it is not possible to try them out "experimentally." The mass, density of the substance of the black hole, the processes of formation of this object, dimensions - all this causes interest among experts, and at times - bewilderment. Consider the topic in more detail. First, we will analyze what such an object is.
general information
An amazing feature of a space object is a combination of a small radius, high density of the substance of a black hole and an incredibly large mass. All the currently known physical qualities of such an object seem strange to the scientist, often inexplicable. Even the most experienced astrophysicists still do not cease to be amazed at the features of such phenomena. The main feature that allows scientists to identify a black hole is the event horizon, that is, the border due to which nothing returns, including light. If a certain zone is permanently separated, the separation border is designated as the event horizon. With temporary separation, the presence of a visible horizon is recorded. Sometimes temporary is a very extensible concept, that is, the area may be separated by a period exceeding the current age of the Universe. If a visible horizon is observed that exists for a long time, it is difficult to distinguish it from the event horizon.
In many ways, the properties of a black hole, the density of the substance that forms it, are due to other physical qualities that are in force in our world. The event horizon of a spherically symmetric black hole is a sphere whose diameter is due to mass. The more mass is pulled inward, the larger the hole. And yet it remains surprisingly small against the background of stars, since gravitational pressure compresses everything inside. If we imagine a hole whose mass corresponds to our planet, then the radius of such an object will not exceed several millimeters, that is, it will be ten billion less than the earth. The radius was named after Schwarzschild, the scientist who first deduced black holes as a solution to Einstein's general theory of relativity.
And inside?
Once in such an object, a person is unlikely to notice a huge density on himself. The properties of the black hole have not been studied well enough to say with certainty what will happen, but scientists believe that nothing special can be revealed when crossing the horizon. This is explained by the equivalent Einstein principle, explaining why the field forming the horizon curvature and the plane-specific acceleration are not different for the observer. Tracking the process of crossing from afar, you can notice that the object begins to slow down near the horizon, as if time in this place flows slowly. After some time, the object crosses the horizon, falls into the radius of the Schwarzschild.
The density of the matter of the black hole, the mass of the object, its dimensions and tidal forces, and the gravitational field are closely related. The larger the radius, the lower the density. The radius increases with weight. Tidal forces are inversely proportional to the weight of the squared, that is, with an increase in size and a decrease in density, the tidal forces of the object decrease. It will be possible to overcome the horizon earlier than notice this fact if the mass of the object is very large. In the early days of the general theory of relativity, it was believed that there was a singularity on the horizon, but it turned out that this was not so.
About Density
As studies have shown, the density of a black hole, depending on the mass, can be more or less. For different objects, this indicator varies, but always decreases with increasing radius. Supermassive holes may appear, which are formed extensively due to the accumulation of material. On average, the density of such objects, the mass of which corresponds to the total mass of several billion luminaries of our system, is less than the density of water. Sometimes it is comparable with the level of gas density. The tidal force of this object is activated after the observer crosses the event horizon. A hypothetical researcher will not suffer, approaching the horizon, and will fall many thousands of kilometers if he finds protection from disk plasma. If the observer does not look back, he will not notice that the horizon is crossed, and if he turns his head, he will probably see light rays frozen at the horizon. Time for the observer will flow very slowly, he will be able to track events near the hole until the moment of death - either it or the Universe.
To determine the density of a supermassive black hole, you need to know its mass. Find the value of this quantity and the Schwarzschild volume inherent in a space object. On average, such an indicator, according to astrophysicists, is extremely small. In an impressive percentage of cases, it is less than the level of air density. The phenomenon is explained as follows. The Schwarzschild radius is directly related to the weight, the density is inversely dependent on the volume, and therefore, the Schwarzschild radius. The volume is in direct proportion to the radius cubed. Mass increases linearly. Accordingly, the volume grows faster than weight, and the average density becomes the smaller, the larger the radius of the studied object.
Curious to know
The tidal force inherent in a hole is a gradient of gravity, which is quite large on the horizon, so even photons cannot fly out of here. Moreover, the increase in the parameter occurs rather smoothly, which makes it possible for the observer to overcome the horizon without risk to himself.
Studies of the density of a black hole in the center of an object are still relatively limited. As established by astrophysicists, the closer the central singularity, the higher the density level. The above calculation mechanism allows you to get a very average idea of what is happening.
Scientists have extremely limited ideas about what is happening in the hole, its structure. According to astrophysicists, the density distribution in the hole is not too significant for an outside observer, at least at the current level. More informative clarification of gravity, weight. The larger the mass, the center and the horizon are more divorced from each other. Such assumptions also sound: immediately beyond the horizon, matter is absent in principle, it can be detected only deep in the object.
Are any numbers known?
About what the density of a black hole, scientists thought for a long time. Certain studies were conducted, attempts were made to calculate. Here is one of them.
The solar mass is 2 * 10 ^ 30 kg. A hole can form at the site of an object that is several times larger than the Sun. The density of the lightest hole is estimated at an average of 10 ^ 18 kg / m 3 . This is an order of magnitude higher than the density of the nucleus of an atom. The difference from the average density level characteristic of a neutron star is approximately the same.
It is possible that ultralight holes exist whose dimensions correspond to subnuclear particles. For such objects, the density indicator will be prohibitively large.
If our planet becomes a hole, its density will be approximately 2 * 10 ^ 30 kg / m 3 . However, scientists have not yet been able to identify the processes as a result of which our space house can transform into a black hole.
About numbers in more detail
The density of the black hole in the center of the Milky Way is estimated at 1.1 million kg / m 3 . The mass of this object corresponds to 4 million solar mass. The radius of the hole is estimated at 12 million km. The indicated density of the black hole in the center of the Milky Way gives an idea of the physical parameters of supermassive holes.
If the weight of an object is 10 ^ 38 kg, that is, it is estimated at about 100 million Suns, then the density of the astronomical object will correspond to the density level of granite found on our planet.
Among all the holes known to modern astrophysicists, one of the heaviest was discovered in the quasar OJ 287. Its weight corresponds to 18 billion luminaries of our system. What is the density of the black hole, scientists calculated without much difficulty. The value is vanishingly small. It is only 60 g / m 3 . For comparison: the atmospheric air of our planet is characterized by a density of 1.29 mg / m 3 .
Where do the holes come from?
Scientists not only conducted research designed to determine the density of a black hole in comparison with the luminary of our system or other cosmic bodies, but also tried to determine where the holes come from, what are the mechanisms of formation of such mysterious objects. Now there is an idea of the four ways of the appearance of holes. The most understandable option is star collapse. When it becomes large, the synthesis in the core is completed, the pressure disappears, the substance falls to the center of gravity, so a hole appears. As you approach the center, the density increases. Sooner or later, the indicator becomes so significant that external objects are not able to overcome the effects of gravity. From this moment a new hole appears. A similar type is found more often than others and is called holes of the solar mass.
Another quite common variant of the hole is supermassive. Such are more often observed in galactic centers. The mass of the object in comparison with the hole of the solar mass described above is more than a billion times. Scientists have not yet established the processes of manifestation of such objects. It is believed that a hole is first formed by the mechanism described above, then neighboring stars are absorbed, which leads to growth. This is possible if the galactic zone is densely populated. The absorption of matter occurs faster than the above scheme can explain, and scientists cannot yet guess how the absorption proceeds.
Assumptions and Ideas
A very difficult topic for astrophysicists is primary holes. These probably come from any mass. They can form in large fluctuations. Apparently, the appearance of such holes took place in the early Universe. So far, studies on the qualities, features (including density) of black holes, the processes of their appearance, do not allow us to determine a model that accurately reproduces the process of the appearance of a primary hole. Currently known models are predominantly such that if they were embodied in reality, an excessively many holes would appear.
It is believed that the Large Hadron Collider can become a source of hole formation, the mass of which corresponds to the Higgs boson. Accordingly, the density of the black hole will be very large. If such a theory is confirmed, it can be considered indirect evidence of the presence of additional measurements. Currently, this speculative conclusion has not yet been confirmed.
Hole radiation
The radiation of the hole is explained by the quantum effects of matter. The space is dynamic, so the particles here are completely different from what we are used to. Near the hole, not only time is distorted; the understanding of a particle largely depends on who observes it. If someone falls into a hole, it seems to him that he is immersed in a vacuum, and for a distant observer it looks like a zone filled with particles. The effect is explained by the stretching of time, space. The radiation of the hole was first revealed by Hawking, whose name was given to the phenomenon. Radiation has a temperature inversely dependent on mass. The smaller the weight of the astronomical object, the higher the temperature (as well as the density of the black hole). If the hole is supermassive or has a mass comparable to a star, the temperature inherent in its radiation will be lower than the microwave background. Because of this, it is not possible to observe it.
The indicated radiation explains the loss of data. This is the name of the thermal phenomenon, which has one distinct quality - temperature. Information about the processes of hole formation through study cannot be found, but the object emitting such radiation simultaneously loses mass (and, therefore, the density of the black hole grows), is reduced. The process is not determined by the substance from which the hole is formed, does not depend on what was drawn into it later. Scientists cannot say what became the base of the hole. Moreover, studies have shown that radiation is an irreversible process, that is, one that simply cannot exist in quantum mechanics. This means that radiation cannot be combined with quantum theory, and inconsistency requires further work in this direction. While scientists believe that the Hawking radiation should contain information, we simply do not yet have the means, the capabilities to detect it.
Curious: about neutron stars
If there is a supergiant, this does not mean that such an astronomical body is eternal. Over time, it changes, discards the outer layers. White dwarfs may appear from the residues. The second option is neutron stars. Specific processes are determined by what is the nuclear mass of the primary body. If it is estimated at 1.4-3 solar, then the destruction of the supergiant is accompanied by very high pressure, due to which the electrons are pressed into protons. This leads to the formation of neutrons, the emission of neutrinos. In physics, it has been called a neutron degenerate gas. Its pressure is such that the star cannot shrink further.
However, studies have shown that probably not all neutron stars appeared that way. Some of them are the remains of large ones that exploded on the basis of the second supernova.
The radius of the body is the smaller, the greater the mass. For most, it varies between 10-100 km. Studies were conducted to determine the densities of black holes, neutron stars. For the second, as shown by tests, the parameter is relatively close to atomic. Specific figures established by astrophysicists: 10 ^ 10 g / cm 3 .
Curious to know: theory and practice
Neutron stars were predicted in theory in the 60-70s of the last century. The first to find pulsars. These are small stars whose rotation speed is very high, and the magnetic field is truly grandiose. It is assumed that the pulsar inherits these parameters from the original star. The rotation period varies from milliseconds to several seconds. The first known pulsars emitted periodic radio emission. Today known pulsars with radiation of the x-ray spectrum, gamma.
The described process of the formation of a neutron star can continue - there is nothing that can prevent it. If the nuclear mass is more than three solar, pointwise the body is very compact, it is referred to as a hole. It will not be possible to determine the properties of a black hole with a mass greater than critical. If due to the Hawking radiation a part of the mass is lost, the radius is reduced at the same time, so the weight value will again be less than critical for this object.
Can a hole die?
Scientists put forward assumptions about the existence of processes due to the participation of particles and antiparticles. The fluctuation of the elements may cause the empty space to be characterized by a zero energy level, which (here is a paradox!) Will not be equal to zero. At the same time, the event horizon inherent in the body will receive the low-energy spectrum inherent in the absolute black body. Such radiation will cause mass loss. The horizon will shrink slightly. Suppose there are two pairs of a particle and its antagonist. An annihilation of a particle from one pair and its antagonist from another takes place. As a result, photons appear that fly out of the hole. The second pair of alleged particles falls into the hole, while simultaneously absorbing a certain amount of mass, energy. Gradually, this leads to the death of a black hole.
In conclusion
According to some, a black hole is a kind of space vacuum cleaner. A hole can absorb a star, it can even “eat” a galaxy. In many ways, the explanation of the qualities of the hole, as well as the features of its formation, can be found in the theory of relativity. It is known from it that time is continuous, as well as space. This explains why the compression processes cannot be stopped, they are unlimited and unlimited.
Such are these mysterious black holes over which astrophysicists have been racking their brains for decades.