What is a black hole?
Black holes are a strange place, and the laws of physics we know here are no longer valid. Einstein pointed out that the gravity of a black hole would be a tortuous time and space, and the formation of time and space itself would be distorted. Therefore, if there is an object with a high density, the space and time will be severely distorted, so that a similar depression is formed in the ideal space and time around the object. This is a black hole. When a massive star runs out of its fuel and the explosion collapses, this process will be enough to produce such a super-compact dense object. When the center of the life of a supermassive star shrinks under its own mass, the time and space around it is distorted. Its gravitational force began to become so strong that the light could not escape its control: a new black hole appeared in the original position of the star.
The outermost layer of the black hole is the boundary of its affairs, and the boundary of the gravitational category where the light just begins to escape. Outside this area, the light can escape, and once it crosses this limit, any effort to escape will be in vain. The boundaries of things contain great energy. The quantum effect here produces a strong stream of high-temperature particles and radiates outward, which is called Hawking radiation. This is named after the famous British astrophysicist Hawking, because he began to predict the existence of this radiation effect. Just give plenty of time, and this Hawking radiation will eventually exhaust the full mass of the black hole and lead to the ultimate extinction of the black hole.
As you gradually deepen the black hole, time and space become more and more distorted until you reach the center of the black hole—where the distortion of time and space reaches an infinite level, which is a singularity. There is no longer a sense of space and time here, and the laws of physics based on the concept of time and space, as we know it, will all fail.
According to theoretical calculations, there are tens of millions of black holes in the Milky Way. The astronomical community believes that many galaxies have supermassive black holes in the center. For example, the mass of the central black hole of the super-large elliptical galaxy code-named M87 is considered to be about 6.5 billion times that of the sun.
Astronomers divide the black holes in the universe into three categories based on mass: constant-star quality black holes , supermassive black holes and medium-quality black holes .