We all know that stars can become black holes after they die, but not every star will become a black hole. This is only possible for stars that are large enough, and the nearest black hole may be less than 100 light years away from the earth. Black holes are not the cosmic vacuum cleaners in science fiction. They don’t go everywhere. You have to look for them, but if you do go there, you will never come back!
When huge stars consume their nuclear fuel, they can no longer maintain high temperatures to counteract their own inward gravitational pull. Massive stars collapse, leaving no light but gravity. Black holes hide the shrunken corpse of a supergiant star, and the star itself It may shrink to a size smaller than a black hole, only a few dozen kilometers across.
The first black hole discovered by scientists was Cygnus X-1. How did we discover it on Earth? An object so small, so dark and so far away! Scientists use another type of light: X-rays! In X-rays, we can no longer see blue stars because its surface temperature is only 30,000 degrees, while the gas disk around the black hole shines brightly in X-rays with a temperature as high as 100 million degrees.
As scientist William Herschel discovered, many stars have close partners to form a binary star system, but if one of them is extremely huge and the other is smaller, the smaller one can swallow up the gas of its brother. This kind of ” The “neurotic relationship” can last for millions of years. The gas from the larger star is pumped to the hot and dazzling accretion disk. The accretion disk keeps spinning and spirals into the black hole. The unstoppable gravity continues to accelerate the blue star’s growth. The gas swept it into the vortex of death, crossing the boundaries of time and never returning.
This crucial boundary separates a black hole from the rest of the universe and is called the event horizon. It appears to us that matter in the accretion disk slows down as it approaches the event horizon, but never touches it. If you stand on an atmospheric vortex, you will cross the event horizon in a few seconds and enter an unknown world from which no one has ever returned!
Scientists have searched the centers of dozens of galaxies and found a supermassive black hole in each one, and our own Milky Way is no exception.
The stars closest to the center of the Milky Way move at a speed of more than 40 million kilometers per hour. Why do they move so fast? The only reasonable explanation is that there is an object with a mass equal to 4 million suns in the center of the Milky Way. Where does the light from these 4 million suns go? Since we can’t see it, it must be fastened inside the black hole! The Earth is far away from the center of the Milky Way and is very safe, but other worlds may not be so lucky!
If you could cross the event horizon alive, you could look back and see the entire future history of the universe unfold before your eyes. Why is that? Because space-time is distorted by the extreme gravity of the black hole, time is stretched to the extreme.