At the invitation of Astrophysics group at the school of physics and technology in NJNU, Professor Yuan Yefei from USTC gave a talk at 3 PM on April 25 in room K2-435 titled “Imaging observation of an supermassive black hole at the center of the nearby galaxy M87 “. Teachers and graduate students in related fields took part in the academic report.
Yuan yefei is a professor and doctoral supervisor in the department of astronomy, school of physics, USTC. In 1999, he graduated from the center for astrophysics of USTC and taught there. He was promoted to professor in 2005 and served as executive director of the department of astronomy. In 2017, he was funded by the national science foundation for outstanding young people. Mainly engaged in the teaching and research work in the field of black hole astrophysics. He is currently executive director of the Chinese astronomical society.
In this report, professor Yuan yefei, starting from Kepler's law and the law of universal gravitation, introduced the difficulties caused by the treatment of the precession of mercury's perihedral orbit by universal gravitation, and thus led to Einstein's general theory of relativity proposed in 1915. Professor Yuan explained the basic hypothesis of general relativity, as well as related physical ideas and effects in a simple way, and proposed that gravity is not a force but a physical effect of space-time bending. Professor Yuan reviewed the physical experiments to verify general relativity in history. Professor Yuan then gave us a brief introduction to the mathematical equations of general relativity, the minkowski metric, the schwarzschild metric and the 'light cone' of flat space. He specially explained the different manifestations of the 'light cone' outside the schwarzschild radius of the black hole, at the schwarzschild radius and inside the schwarzschild radius. Professor Yuan also introduced the Kerr metric, the concept of Kerr black hole 'energy layer' and the Penrose process of extracting rotational energy from the black hole. Since then, professor yuan has interpreted images of the supermassive black hole at the center of the neighboring galaxy M87, with its central shadow and north-south brightness asymmetry, and compared them with theoretical physics work. Finally, professor Yuan also introduced the EHT plan of VLBI technique and concrete used in observation, with intuitive observation showing us interference in VLBI technology base and the importance of the number of telescope, as well as briefly introduces the EHT plans to radio observations from the 1.3 mm push to 0.8 mm observation in the future, in order to get better spatial resolution. After the end of the report, teachers and students responded enthusiastically and raised a lot of questions related to the black hole pictures in a broad sense. In particular, the negative energy particles in the black hole energy layer during Penrose's process aroused the interest of many students. Professor yuan answered these questions in detail and welcomed students to contact and communicate him further.