Chinese scientists have discovered a millisecond pulsar PSR J1928+1815 in the Milky Way using the "Chinese Eye". It is obscured by a companion star for one sixth of the time (i.e. occultation), and its mass far exceeds that of a typical occultation pulsar. This type of occultation pulsar is very rare and of great significance for studying stellar evolution, dense star accretion, binary star mergers, and gravitational wave sources. This discovery was completed by Han Jinlin, a researcher at the National Astronomical Observatory of the Chinese Academy of Sciences, and the paper was published online in the international academic journal Science in the early morning of May 23. In the vast Milky Way galaxy, most stars appear in pairs and evolve together. How does material exchange occur between binary stars? What is the process of evolution? It has long been a cutting-edge topic in astronomy. ”Han Jinlin said. The theory of binary evolution suggests that stars with higher mass generally evolve first and collapse into high-density compact stars, such as pulsars or black holes. The material of companion stars with small mass will be accreted by dense stars, and their volume will expand due to mass loss, even to the point where they will "embrace" the dense star. Afterwards, the binary star evolved in a common envelope for about a thousand years. After the evolution of the common envelope, dense stars and high-temperature helium stars with rapid rotation are left to orbit each other in very tight orbits. However, the survival time of such special binary systems generated after the evolution of the common envelope is only about 10 million years, and then the companion star evolves into a white dwarf, entering a new stage. For the 13.8 billion year universe, this time is fleeting. It is estimated that there are only a few dozen binary star systems in the Milky Way, which is extremely rare and therefore difficult to capture. ”Han Jinlin said. In 2020, the team used the "Chinese Eye" to conduct a deep search of pulsars in the Milky Way and discovered PSR J1928+1815, with a rotation period of 10.55 milliseconds. Its orbit around its companion star has a period of only 3.6 hours, and its companion star has a mass at least the size of one sun. Based on these results, it can be inferred that its companion star should be a high-temperature helium star. The occultation of pulsar signals is caused by the obstruction of stellar wind material thrown out by helium stars. ”Han Jinlin said that this pulsar and companion star should be a special binary star that has undergone a common envelope evolution. The reviewer of Science believes that this discovery has extremely high scientific value, which will help scientists better conduct research on the evolution of the common envelope of binary star systems, and is expected to provide observational basis for scientific research in multiple fields such as stellar population evolution, dense star accretion, and gravitational wave source prediction. (New Society)