Nature astronomy, a famous international journal, published the latest observation results of HXMT satellite online: the low-frequency quasi periodic oscillation (QPO) of black hole binary system was found in the energy band higher than 200 keV, which is the highest low-frequency QPO phenomenon found so far. The results show that it originates from the precession of relativistic jet (plasma flow moving outward at high speed) near the event horizon of black hole, which provides an important basis for solving the controversial physical origin of low-frequency QPO. < / P > < p > the research work was jointly completed by researchers from Institute of high energy, Chinese Academy of Sciences, University of Southampton, University of Tubingen, Germany, Shanghai Observatory of Chinese Academy of Sciences. < p > < p > low frequency QPO was discovered in the 1980s. It is a time-varying phenomenon in X-ray binaries, which is similar to periodic but not precise periodic modulation on the light variation curve. For more than 30 years, the origin of low-frequency QPO has been an unsolved problem in the study of compact objects. At present, there are two kinds of most popular models to explain the low-frequency QPO phenomenon, that is, the instability on the accretion disk formed in the process of matter rotating and falling towards the black hole causes the X-ray radiation to oscillate, or the precession or oscillation of the coronal X-ray radiation region near the black hole causes the X-ray radiation to produce quasi periodic modulation. However, before Huiyan satellite, X-ray satellite only has the ability to study low-frequency QPO in the energy region below 30 keV, so it is difficult to distinguish these models. The effective energy range of comet satellite is 1-250 keV, and has the largest effective area above 30 keV. Scientists expect that the low-frequency QPO phenomenon above 30 keV can be detected by comet in some black holes, so as to test the relevant theoretical model more strictly. < / P > < p > on March 11, 2018, the black hole X-ray binary (a binary system composed of a black hole several times the mass of the sun and a star) maxij 1820 + 070 broke out, which was one of the brightest X-ray sources in the sky for a long time. With the rapid response of Huiyan satellite, the high-frequency fixed-point observation of this important object has been carried out for several months, and a large amount of observation data have been accumulated. Based on these observational data, the team found that there was a low-frequency QPO phenomenon in maxij1820 + 070 over a wide energy range, with a maximum energy of more than 200 KeV is almost an order of magnitude higher than that of QPO before the comet, which indicates that the QPO does not come from the thermal radiation region of the accretion disk; further studies also show that the frequency and amplitude of QPO do not change with energy, and the lower energy QPO is produced later than the higher energy QPO, which is in serious conflict with the existing popular models. Therefore, the research team proposed that the low-frequency QPO should be generated by the precession of the jet near the event horizon of the black hole, which is probably caused by the drag effect of the general relativity reference frame produced by the rotation of the black hole. < p > < p > jet is a kind of high-speed material flow that moves close to the speed of light. It has been observed in many black hole X-ray binaries and distant quasars with supermassive black holes (mass of one million to ten billion times the mass of the sun) in the radio, visible and X-ray bands. It is a main observation feature of black hole systems and it is also the phagocytosis of surrounding materials by black hole systems The process is a major means to produce significant feedback on the surrounding environment. However, these jets are very far away from the black hole (usually located at a distance of more than one million times the horizon radius of the black hole, where the black hole’s gravity actually has no effect), it is not clear how far away these jets originate from the black hole, and how they escape from the black hole’s strong gravitational field and are accelerated to near the speed of light. For the first time, the source of the jet is located hundreds of kilometers away from the black hole (several times the horizon radius of the black hole). This is the closest relativistic jet to the black hole. It is of great significance to study the general relativistic effect, matter dynamics process and radiation mechanism near the black hole. The research results of comet satellite on low and medium frequency QPO phenomena in maxij1820 + 070 show its strong ability to study the fast variability of high-energy X-rays. In the future, more high-energy and low-frequency QPO phenomena are expected to be discovered by the comet satellite, which will deepen people’s understanding of the low-frequency QPO phenomenon. The Huiyan satellite is the first space X-ray astronomy satellite in China. The Institute of high energy and energy is the proponent of the project, and takes charge of the satellite payload, ground application system and scientific research. The Fifth Academy of Astronautics is responsible for the work of satellite system and the research of satellite platform. Tsinghua University and National Space Science Center of Chinese Academy of sciences are also involved in the Huiyan satellite project Xin, Beijing Normal University, etc. Chinese version of K-car: reading a10e design drawing exposure