A black hole is a mysterious celestial body whose gravitational pull is so strong that not even light can escape. Therefore, the black hole itself is invisible, and it can only be discovered and studied through its impact on the surrounding matter. Black holes have many peculiar properties, such as distorting space-time, producing gravitational lensing, emitting Hawking radiation, etc. To understand the nature of black holes, it is necessary to photograph the ** of black holes. However, it is very difficult to photograph the ** of a black hole because the black hole is too small, too far away, and too faint. To see black holes clearly, you need a very powerful telescope with a resolution tens of millions of times higher than that of the human eye.
To achieve this, an international collaboration called the Event Horizon Telescope (EHT) uses multiple radio telescopes on Earth to combine them into a virtual megascope through a technique called interferometry. The diameter of this virtual telescope is equal to the diameter of the Earth, and its resolution is high enough to see the shadow of a black hole.
In April 2017, the project observed two supermassive black holes, located at the center of the M87 galaxy and the Milky Way. In 2019 and 2022, the project published the ** of these two black holes, respectively, which is also the first time in human history that black holes have been directly photographed**. These ** show a bright ring structure around the black hole, which is produced by the gravitational lensing effect of the black hole. The inner edge of this annular structure is the event horizon of the black hole, which is the shadow of the black hole. The size and shape of this shadow can verify the performance of Einstein's general theory of relativity under extreme conditions, and can also provide clues for studying the information and properties of black holes.
The process of photographing these ** is not simple, and it requires overcoming many technical difficulties, such as how to synchronize time and frequency between different radio telescopes in order to accurately measure and record the faint signals emitted from black holes.
How to transfer and store massive amounts of data between different geographic locations for subsequent processing and analysis.
How to reconstruct images of black holes from noise and interference using sophisticated algorithms and artificial intelligence techniques, and how to verify and optimize the quality of the results.
These are very difficult and time-consuming tasks that take years and tens of millions of dollars in funding. However, the project eventually did, showing humanity a miracle that had never been seen before, a mystery beyond imagination, and an achievement that changed history.