591 High Velocity Stars

591 high velocity stars’ positions and orbits. Credit: Kong Xiao of NAOC

A research team, led by astronomers from National Astronomical Observatories of Chinese Academy of Sciences (NAOC), has discovered 591 high velocity stars from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) and Gaia, and 43 of them can even escape from the Galaxy. After the first high velocity star was found in 2005, there remain in overall of over 550 high speed stars have actually been discovered with numerous telescopes in 15 years. “The 591 high speed stars found this time doubled the overall number of high speed stars formerly discovered, bringing the total number going beyond 1000,” stated Dr. Yin-Bi Li, the lead author of the research study.

High speed stars are sort of fast-moving stars, and they can even leave from the Galaxy. “Though uncommon in the Milky Way, high speed stars, with special kinematics, can offer deep insight into a wide range of Galactic science, from the main supermassive great void to distant Galactic halo,” said Prof. You-Jun Lu from NAOC, co-author of this research.

As discussed above, these high velocity stars were discovered with LAMOST and Gaia. LAMOST is the largest optical telescope in China, which has the greatest spectral acquisition rate on the planet and can observe about 4,000 celestial targets in one single direct exposure, and it started the routine surveys in 2012, which established the biggest spectra database in the world. Gaia is a space-based mission in the science program of the European Space Firm (ESA) launched in 2013, and it provided astrometric specifications for over 1.3 billion sources, which is the biggest database of astrometric criteria. “The two huge databases provide us unmatched chance to find more high speed stars, and we did it,” said Prof. A-Li Luo from NAOC, co-author of this research.

From the kinematics and chemistries, research study group discovered that the 591 high speed stars are inner halo stars. “Their low metallicities show that the bulk of the stellar halo formed as a consequence of the accretion and tidal interruption of dwarf galaxies,” stated Prof. Gang Zhao from NAOC, co-author of this research.

The discovery of these high speed stars tells us that the combination of numerous large surveys in the future will assist us to discover more high velocity stars and other uncommon stars, which will be used to study the unsolved secret about our Galaxy.

This work has actually been just recently published online in The Astrophysical Journal Supplement Series

Reference: “591 High-velocity Stars in the Galactic Halo Selected from LAMOST DR7 and Gaia DR2” by Yin-Bi Li, A-Li Luo, You-Jun Lu, Xue-Sen Zhang, Jiao Li, Rui Wang, Fang Zuo, Maosheng Xiang, Yuan-Sen Ting, Tommaso Marchetti, Shuo Li, You-Fen Wang, Shuo Zhang, Kohei Hattori, Yong-Heng Zhao, Hua-Wei Zhang and Gang Zhao, 17 December 2020, The Astrophysical Journal
DOI: 10.3847/1538-4365/ abc16 e

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