The black hole imaging research team of the Shanghai Observatory of the Chinese Academy of Sciences is working diligently towards the sea of ​​​​stars to occupy a place at the forefront of black hole research in the world——

"Dialogue" with the black hole that freezes the universe

Our reporter Pei Longxiang

　　"Worker Daily" (Page 05, April 8, 2024)

　　What kind of mysterious existence is a black hole? Thanks to a photo, human beings’ understanding of it has become concrete step by step——

　　In April 2019, the first human photo of a black hole taken by the Event Horizon Telescope (EHT) - a photo of the supermassive black hole at the center of the M87 galaxy was released, shocking the world;

　　Three years later, the photo of the black hole at the center of the Milky Way taken by the EHT was released for the first time, verifying Einstein's general theory of relativity from the perspective of a strong gravitational field;

　　Less than a year later, an international research team captured the first "panoramic photo" of the black hole of M87. The black hole's shadow, accretion disk and jets were all frozen in one photo at the same time.

　　These three iconic photos show the growth of the black hole imaging research team of the Shanghai Observatory of the Chinese Academy of Sciences from active participation to occupying a place at the forefront of world black hole research. "Astronomy is undoubtedly romantic, but researchers mostly work in obscurity for a long time." Shen Zhiqiang, director of the Shanghai Observatory of the Chinese Academy of Sciences, described the team looking up at the stars.

Breaking the research “ceiling”

　　In 1997, Shen Zhiqiang graduated with his Ph.D., and "seeing" black holes seemed to have infinite appeal to him. "At that time, I had to wait 20 months before I could have a five-hour observation opportunity."

　　In the following five years, he and his colleagues carried out more than 20 high-resolution VLBI (very long baseline interferometry) observations, and each step of the work represented the latest progress in the field at that time. In 2005, Shen Zhiqiang led an international astronomical research team to publish the world's first high-resolution image of the black hole at the center of the Milky Way at a wavelength of 3.5 millimeters in Nature magazine.

　　"When I returned to China, I wanted to advance domestic black hole imaging research to the internationally advanced level." Along the way of his studies, Lu Rushen always kept the wishes of his mentor Shen Zhiqiang in mind. In 2018, he returned to China with years of research accumulation and joined the Radio Astronomy Science and Technology Laboratory of Shanghai Observatory.

　　"Science needs debate, the existing research 'ceiling' needs to be broken, and the 'Chinese voice' needs to be heard." Lu Rushen held back his motivation and focused on carrying out the most cutting-edge international research based on the existing research of the Shanghai Observatory. Millimeter wave band imaging research.

　　In 2023, he led an international team to complete imaging research on the M87 black hole and its surrounding environment, capturing photos of the black hole in a new waveband for the first time, achieving a breakthrough in taking a "panoramic photo" of the "central engine" of the active galactic nucleus. After the research results were published in the journal Nature, they attracted widespread attention around the world.

"Expensive" calculations

　　If you want to see a black hole from the earth, you must use a telescope working in the submillimeter waveband. Submillimeter astronomical observations require dry weather conditions and a thin atmosphere. Therefore, dormant volcanic craters in Hawaii have become a holy place for astronomical observations.

　　Jiang Wu, an associate researcher at the Radio Astronomy Science and Technology Research Office of the Shanghai Observatory, was fortunate enough to go to the site to participate in the observations of the Event Horizon Telescope. "Apart from the asthma and a little headache caused by altitude sickness, the most impressive thing is that although the observation was in the middle of the night, everyone was very enthusiastic and worked meticulously." Jiang Wu recalled that sometimes on his way back to the base in the early morning, he would see other people The sparks emerging from the crater were deeply shocked by the power of nature.

　　Zhao Shanshan is a young researcher born in the 1990s in the Shanghai Observatory’s high-resolution radio astrophysics research group. Her theoretical working group needs to compare the model image library with observational data to select the optimal model.

　　The environment around a black hole is very complex, resulting in uncertainty in many physical parameters. Each model image requires a lot of manpower and computing power. A numerical simulation requires several weeks to several months of calculations on a supercomputer, and must be recalculated if the parameters change. "From this perspective, the theoretical explanation of black hole images is very 'expensive'." Zhao Shanshan said.

Make a "movie" about a black hole

　　"In the past, I thought that doing scientific research meant sitting in front of the computer, pushing formulas and writing codes. I never thought that I could participate in building telescopes." In order to use my country's own equipment to take pictures of black holes as soon as possible, Zhao Shanshan followed the team to Tibet. Investigate and find a suitable site.

　　"In order to seize the commanding heights in the next step of research on making 'movies' of black holes and have more international academic voice, we must have our own observation equipment." Lu Rushen knows that there is still a long way to go in the future. To this end, the Shanghai Observatory has promoted the construction of my country's millimeter wave VLBI experimental system, actively promoted the construction of submillimeter wave telescopes and arrays in the western region, and developed related observation facilities.

　　Jiang Wu is also working hard to promote the construction of submillimeter wave telescopes. "Multi-frequency simultaneous reception technology is the future development trend. It can detect weaker signals, so it is expected to observe more black hole images."

　　"The public is very interested in our research results and always asks a lot of questions. At this time, I will truly feel that it is human nature to explore the unknown." Zhao Shanshan said that as the "advance team" to explore black holes, he will bring the latest It is the responsibility and obligation to bring scientific research results to the public, and I also reap the joy of sharing through communication.