China News Agency, Beijing, March 24 (Reporter Sun Zifa) How old is the Milky Way?

How did it form and evolve?

The internationally renowned academic journal "Nature" published the latest research results of astronomers in the form of a cover article on March 24, Beijing time. The paper pointed out that the Milky Way may have gone through different stages of evolution, starting with the formation of disk stars about 13 billion years ago.

　　The result of this major astronomical study comes from the precise calculation of the ages of nearly 250,000 stars and was done in collaboration with Dr Xiang Maosheng and Professor Hans-Walter Rix at the Max Planck Institute for Astronomy in Germany.

Based on the survey observations of the Guo Shoujing Telescope (Large Sky Area Multi-Object Fiber Spectroscopic Astronomical Telescope, LAMOST) operated by the National Astronomical Observatory of the Chinese Academy of Sciences and the Gaia Telescope (Gaia), the European Space Agency's astrometric satellite, they obtained the most Accurate and large-sample stellar age information clearly restores images of the formation and evolution of the Milky Way during its infancy and youth according to time series, rewriting people's understanding of the early formation history of the Milky Way.

　　In order to study the formation history of the Milky Way, the two astronomers identified about 250,000 stars in the subgiant stage from telescope survey data, the space volume of which accounts for a large part of the Milky Way.

They estimated the individual ages of these stars to range from 1.5 billion to 13.8 billion years, and subsequent studies confirmed and characterized the origin of different structural elements in disk and halo stars. The results showed that the formation of the Milky Way's thick disk occurred at about It started 13 billion years ago, just 800 million years after the Big Bang.

　　The latest research shows that in terms of time, the integration and evolution history of the Milky Way is divided into two distinct stages, from the early stage from 13 billion years ago to 8 billion years ago and the late stage from 8 billion years ago to the present, the early stage formed the Milky Way. Thick disk and halo, late stage formation of the Milky Way thin disk.

　　"Nature" published a "News and Views" article by American astronomers at the same time that the age, composition and motion of stars in this study reflect the dynamic process of the formation of the Milky Way, and more data will lead to a larger sample size of stars in the Milky Way. , making people's understanding of the formation of the Milky Way clearer and clearer.

　　The National Astronomical Observatory of the Chinese Academy of Sciences stated that in this study on the origin and evolution of the Milky Way, the Guo Shoujing telescope released tens of millions of stellar spectral data, which became the cornerstone of the digital galaxy, and the Gaia satellite provided the location and moving maps of 1.4 billion stars. "It provides astronomers a unique advantage in tracing the integration and evolution history of the Milky Way.

At the same time, thanks to the Guo Shoujing Telescope Galaxy Survey and other international survey projects, obtaining the age of a large sample of stars has gradually become a reality in the past few years, which is a landmark step for the study of the formation and evolution of the Milky Way.

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