China News Service, Shanghai, February 12: Title: The Shanghai Observatory team of the Chinese Academy of Sciences talks about "Black Hole Photography": Humanity is both great and small

　　China News Service reporter Zheng Yingying

　　"The M87 black hole is 55 million light-years away from us, which means that the light we see was actually emitted 55 million years ago. This makes me feel that human beings are both great and very small." said Shen Zhiqiang, Director of the Shanghai Observatory of the Chinese Academy of Sciences .

The first human photo of a black hole. (Image source: EHT Partnership)

　　Lucky times: With the "weapon for observing the universe"

　　In April 2019, a major astronomical achievement completed by the cooperation of more than 200 scientists around the world - mankind's first black hole photo was released simultaneously in many places around the world. Among the more than 200 scientists at that time, 16 were from mainland China, including 8 from the Shanghai Observatory of the Chinese Academy of Sciences.

　　“I don’t know the true face of Mount Lu, just because I am in this mountain.” Shen Zhiqiang said in a recent interview. Recalling the process of releasing mankind's first black hole photo, he lamented that it is difficult to take a photo of a black hole, and it is even more difficult to capture a photo of the black hole in the center of the Milky Way. There are many challenges in how human beings in the Milky Way can "see through" the solar system and "see" the black hole at the center of the Milky Way through the galactic disk.

　　He explained that Einstein's general theory of relativity had long predicted the existence of black holes, but more than 100 years ago, no matter how smart the Earthlings were, they could not observe black holes due to their immature technology.

　　Science and technology are closely connected. Only with the "weapon for observing the universe" can black hole photos be released. This "cosmic observation tool" uses 8 ground-based radio telescopes (synchronous observations) around the world and the rotation of the earth to form a "virtual" telescope with an aperture the size of the earth. From this, the first, second and even more black hole photos were released.

　　Global Wisdom: Two Black Hole Photos in a Row

　　In Shen Zhiqiang's view, mankind's first black hole photo is a model of global teamwork. Researchers from all over the world have set the scientific goal of searching for black hole photos for more than ten years and created the EHT (Event Horizon Telescope) cooperative organization to capture black holes. Image.

　　In fact, scientists were targeting two black holes at that time, one was the black hole at the center of the Milky Way, and the other was the black hole at the center of the M87 galaxy. The former is close to the earth, but has a small mass, and the latter is far from the earth, but has a large mass, so the two black holes are about the same size when viewed from the earth. The black hole at the center of the Milky Way is "fickle" because of its small mass. It moves every few minutes, making it difficult to photograph. As a result, the black hole at the center of the M87 galaxy, which moves for dozens of days, took the lead in having the first "black hole identity photo" taken by humans. Following 2019, in May 2022, mankind finally announced that it had "taken" a second black hole photo - the "fickle" supermassive black hole "Sagittarius A* (Sgr A*)" located in the center of the Milky Way. The photos were also "developed".

　　As a member of the "Black Hole Photography Team", Lu Rushen, a researcher at the Shanghai Observatory of the Chinese Academy of Sciences, said that the story of taking pictures of black holes is not over. The Shanghai Observatory team of the Chinese Academy of Sciences is promoting the construction of relevant domestic facilities and hopes to continue to take pictures of black holes in the future. A "movie" composed of pictures. He pointed out that in order to seize the commanding heights of science and technology and win more international academic voice in the next step of research on shooting "movies" on black holes, the Chinese scientific research team needs to have its own observation equipment. The Chinese scientific research team has promoted the construction of millimeter-wave VLBI (Very Long Baseline Interferometry) experimental systems, and is also promoting the construction of submillimeter-wave telescopes and arrays in western China.

　　Endless exploration: scientific research has no end

　　To see a black hole from Earth, a telescope operating in the submillimeter wavelength band is necessary. Submillimeter astronomical observations require dry weather conditions and a thin atmosphere, so craters are a good choice. Jiang Wu, a member of the "Black Hole Photography Team" and an associate researcher at the Shanghai Observatory of the Chinese Academy of Sciences, once observed black holes in a volcanic crater in Hawaii, USA.

　　"The biggest benefit is that sometimes after observing a black hole, on the way back in the early morning, I see Mars erupting from the crater on another mountain. I feel that I have caught up with the magic of the black hole in the universe and the magic of nature at the same time." Jiang Wu recalled explain.

　　Astronomy, the study of the vast universe, has a following. Zhao Shanshan, an assistant researcher at the Shanghai Observatory of the Chinese Academy of Sciences, is a "post-90s generation". She deeply feels lucky to be able to take photos of black holes. "My work not only satisfies my need to explore the unknown, but everyone's attention to black holes also allows me to realize social value." " Dealing with black holes makes her find it interesting. She said that in fact, celestial bodies are as complex as people and are undergoing many changes. "If you are 'reborn' as a black hole, you may also experience the troubles of a black hole."

　　Humanity's first and second black hole photos have been released, each time attracting international attention, and the team members are also honored. Shen Zhiqiang deeply feels the team's luck, "If we can get some results, it will be the greatest compliment. If we don't catch up (results release), it doesn't matter. I have to recognize my own research in my heart."

　　In his view, scientific research itself is a very interesting thing, because scientific researchers are always pursuing the ultimate while opening up more research fields; for example, after the first picture of a black hole, there is a second picture, and future scientific research Crews can also observe more, including double black holes.

　　"Scientific research never ends," he said. (over)