Recently, Xu Ye's research team at the Zijinshan Observatory of the Chinese Academy of Sciences and the National Astronomical Observatory of the Chinese Academy of Sciences jointly proposed a new understanding of the spiral arm shape of the Milky Way: the Milky Way is more like an ordinary multi arm galaxy, which is composed of two internal symmetric spiral arms and several external irregular spiral arms, rather than the previously widely accepted special shape of four spiral arms from inside to outside. This research result has changed people's traditional understanding of the spiral arm structure of the Milky Way, and was published online in The astrophysics Journal under the title "What Does the Milky Way Look Like?". Since its publication for over half a month, the paper has been downloaded more than 2800 times, making it one of the ten most read papers in the journal and attracting widespread attention from researchers and the public worldwide. It is reported that the morphology of spiral galaxies in the universe is mainly divided into three types of vortex structures: macroscopic, multi spiral arms, and flocculent. In multi spiral arm galaxies similar to the Milky Way, the most common forms are the inner two spiral arms and the outer multi spiral arms (approximately 83%). The form of all four spiral arms from the inside out is very rare (approximately 2%), and previously, the astronomical community generally believed that the Milky Way belongs to this latter special form. Due to the fact that humans are located in the Milky Way, multiple structures overlap in the line of sight, making it impossible to directly observe the shape of the Milky Way from a "bird's-eye" perspective. The research team comprehensively used all high-precision astrometry data available at present, and used celestial masers, young stars and open star clusters as the "lighthouses" for positioning the spiral arms to re depict the structure of the spiral arms of the Milky Way. The research results show that the Milky Way Galaxy has a multi spiral arm shape, and its inner part extends symmetrically from the Perseus Arm and the moment arm, which bifurcates outside and forms a number of long and irregular spiral arms, including the centaur arm, the centaur arm, the bottom arm and the local arm. This makes the Milky Way no longer look special. For more than 20 years, Xu Ye and his collaborators have achieved an epoch-making breakthrough in high-precision astrometry through technological innovation, and made systematic and innovative work in the field of galactic structure. In 2006, Xu Ye and the project team successfully measured the distance of the Perseus Arm of the Galaxy for the first time, with a measurement accuracy of 2%, which is the most accurate distance measurement of distant objects in astronomy. This research achievement was listed on the cover of Science magazine, and became the first show of research achievements of Chinese astronomers as the lead author on the cover of the magazine. Binney, a member of the Royal Society of England, published a special article in the journal Science, commenting that the achievement "ushered in a new era of triangular parallax measurement". The successful measurement of the Perseus Arm distance has triggered an upsurge of global astronomers and telescopes to use trigonometric parallax to measure and study the structure of the Milky Way. The research led by Xu Ye has overturned the traditional understanding of the spiral arm structure of the Milky Way and opened up a new level of research on the structure of the Milky Way. In 2011, the relevant achievements were evaluated as a "milestone" in this field by the authority on galactic research Caswell; In 2016, it was commented by Science magazine as "depicting the spiral arm structure near the sun in unprecedented detail"; Published in the Journal of the American Academy of Sciences as the Milky Way in 2021
Edit：Hou Wenzhe Responsible editor：WeiZe
Source：people.cn
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