There are 200 billion to 400 billion stars in the Milky Way, but how many black holes are there? There are hundreds of millions of black holes.
What is a black hole?
A black hole is a celestial body that exists in the universe according to the modern general theory of relativity. The gravitational pull of a black hole is extremely strong, causing the escape velocity within the event horizon to be greater than the speed of light. Therefore, “a black hole is an object whose curvature of space-time is so great that even light cannot escape from its event horizon.”
Black holes were first theoretically speculated and predicted.
In 1916, German astronomer Karl Schwarzschild obtained a vacuum solution to Einstein’s gravitational field equation through theoretical calculations. This solution shows that if the actual radius of a static spherically symmetric star is less than a fixed value, a strange phenomenon will occur around it, that is, there will be an interface – an “event horizon”. Once it enters this interface, even light cannot escape. This constant value is called the Schwarzschild radius, and this incredible celestial body was named a black hole by American physicist John Wheeler.
Black holes cannot be observed directly. However, information about the existence of a black hole can be obtained indirectly through the “edge information” of X-rays and gamma rays emitted due to the friction caused by the acceleration caused by the black hole’s gravity before the objects around it are sucked in.
At 21:00 on April 10, 2019, Beijing time, the first photo of a black hole was released. The black hole is located in the center of M87, a giant elliptical galaxy in the constellation Virgo. It is 55 million light-years away from the earth and has a mass of about 6.5 billion times that of the sun. At 10 pm on March 24, 2021, Beijing time, the image of the M87 supermassive black hole under polarized light was released.
Although our understanding of black holes is still limited, we know that it is a “death place” with huge space curvature, huge mass density, and strong gravity. Nearby stars and light will eventually fall in and disappear without a trace. trace.
If we want to travel across the galaxy through interstellar space, we must find the location of each black hole and map out a safe path for travel. Can this be done?
See how the first black hole photo was taken.
The black hole at the center of our Milky Way Galaxy, Sagittarius A*, requires a telescope 1,000 times more powerful than Hubble to get enough resolution to see it. An international organization called EventHorizonTelescope is trying to solve this problem. It has created a joint measurement method that combines telescopes around the world to simulate a virtual telescope equivalent to the size of the entire Earth. In April 2017, astronomers mobilized nine observatories around the world to conduct a joint operation, using interferometry to collect radio signals with millimeter wavelengths. After processing by supercomputers, they obtained not photos in the traditional sense, but Photographs of “radio light” imaging. Two years later, the photo was released to the world, roughly showing the black hole’s “event horizon” – the area from which light cannot escape.
The closest Milky Way star to Earth, Alpha Centauri (αCen), is Proxima Centauri, which is also 4.3 light-years away. According to Einstein’s mass-energy equation E=mc2, even if the spacecraft is small and light, in order to achieve interstellar navigation, it must be accelerated to as close to the speed of light as possible. In this way, the energy required by the spacecraft is immeasurable.
If a spacecraft wants to fly out of the solar system, it must break away from the gravitational constraints of the solar system, which requires at least the third universe speed of 16.7 kilometers/second. To cross the Milky Way, you need to get rid of the gravitational constraints of the Milky Way. Unfortunately, the fourth cosmic speed of escaping from the Milky Way is not yet known exactly. Because we don’t know the exact mass of the Milky Way.
The scientists will publish their latest research results in detail in the Astrophysical Journal. It has been previously estimated that the mass of the Milky Way is between 750 billion and 2 trillion times the mass of the Sun. Now, scientists have established a more accurate model and calculated that the mass of the Milky Way should be about 1 trillion times the mass of the sun. The mass of the Milky Way is made up of hundreds of billions of stars, gas, dust and mysterious dark matter. The exact value cannot be determined.
It can be seen from this that Liu Cixin’s “Three-Body” and “The Wandering Earth”, the American blockbuster “Interstellar”, etc. are all just science fiction. The radius of the solar system is about 6 billion kilometers, and it takes about 6 hours to fly out at the speed of light. The sun is located 2/3 of the way from the center of the Milky Way. It would take about 2314800000 years to fly out of the Milky Way at the speed of light. The fastest speed of human beings, take rockets as an example. Currently, the fastest rocket can reach 7.9 kilometers/second, and it takes about 13 hours to fly out of the Earth-Moon system, not to mention the solar system and the Milky Way. It must be an astronomical figure that is unthinkable. .
Therefore, not only is it impossible for humans to get out of the Milky Way, but whether they can get out of the solar system is also a big question. I said in another article that humans should just stay on earth. We people on earth are facing enough troubles now, so let’s protect our only home. At least in the Milky Way, there are no Earth-like planets that can support life, let alone aliens. Let Musk do the dream of immigrating to Mars. I think his dream is also a fantasy.