The reporter learned from the National Astronomical Observatory of the Chinese Academy of Sciences recently that Chinese astronomers found an ejected star in the globular cluster of the Milky Way, with an ejection speed of up to 550 km/s. Researchers believe that such a high escape velocity is likely due to the presence of a medium mass black hole at the center of the star cluster. This discovery provides new evidence for the existence of intermediate mass black holes. The relevant research results were published in the form of cover articles in the National Science Review. There are two known types of black holes in the universe: stellar level black holes formed by the collapse of massive stars and supermassive black holes located at the center of galaxies. However, medium mass black holes with masses between the two have never been confirmed. They were supposed to be a necessary stage for stellar black holes to grow into supermassive black holes, but astronomers have only found a few questionable candidates so far. Astronomers believe that globular clusters are most likely to harbor intermediate mass black holes. The Hubble Space Telescope once observed that there may be a black hole with a mass of 1700-3200 times that of the Sun at the center of the globular cluster M15, but this result was questioned by many astronomers after its release. They believe that the observational data comes from a range of 5200 times the distance between the sun and the earth from the center of M15, where thousands of dense stars may be clustered rather than a single black hole. In recent years, scientists have discovered seven high-speed stars in another star cluster, speculating that these stars may be related to intermediate mass black holes, but they are located more than 1000 times the distance between the center of the cluster and the Earth. "How to detect a medium mass black hole as close as possible to the center of the globular cluster becomes the last link in the evidence chain to determine the existence of a medium mass black hole." Huang Yang, co first author and corresponding author of the paper and associate professor of the National Astronomical Observatory of the Chinese Academy of Sciences/University of the Chinese Academy of Sciences, said. According to the analysis of the research team of the National Astronomical Observatory of the Chinese Academy of Sciences, if a medium mass black hole exists, when it encounters a nearby binary system at close range, its powerful gravity will act like a slingshot, ejecting a star in the binary system at high speed. They used observation data from the Gaia satellite and the Guo Shoujing telescope to screen out nearly a thousand high-speed "galloping" stars and over a hundred globular clusters in the Milky Way. Unexpectedly, they discovered that the star numbered J0731+3717 was ejected from the globular cluster M15 at a speed of 550 kilometers per second 20 million years ago. This ejected star also carries chemical composition and age characteristics identical to M15. Astronomers have calculated that in order for a star to reach this extreme speed, an object with a mass equivalent to 2000 solar masses must exert gravity at a distance of only 1 time the distance between the Sun and Earth. This location cannot be crowded with thousands of neutron stars or small black holes. The only reasonable explanation is that there is a medium mass black hole lurking here, "Huang said. This discovery is like catching a" cosmic slingshot operator "who is" committing a crime "at the center of the star cluster, opening up the last link in the chain of evidence for the existence of medium mass black holes. (New Society)