An international Astrometry project, named Bar and Spiral Structure Legacy (BeSSeL), investigated the structure of the Milky Way with the technology called VLBI maser astrometry in the past of 15 years. Recently, a study published in Scientific American shared a new view of the Milk Way.
The study was led by Prof. Mark J. Reid, a senior radio astronomer from Harvard & Smithsonian Center for Astrophysics and ZHENG Xingwu, a professor of astronomy from Nanjing University in China and Prof. Karl Menten, the Executive Director of Max-Plank Institute for Radio Astronomy.
As one co-author of this study, Prof. WU Yuanwei, from the National Time Service Center (NTSC) of the Chinese Academy of Sciences, has spent more than 10 years on this project. He led the study of the Sagittarius arm, and for the first time pinpointed that the location of the Sagittarius arm far (~ 10 kpc) beyond the tangent point of the arm, one of the major spiral of our Galaxy. This study is a substantive part of the project. Related results were published in Astrophysics Journal in 2019.
In this project, the researchers measured about 200 parallax-based distances for young hot stars across large regions of the Milky Way. These data, which give good coverage of about one third of the Milky Way, revealed at least four major spiral arms in the Milky Way, as well as some smaller features, and showed that the sun lies almost exactly on the central plane of the disk of the galaxy.
By modeling the motions of these massive stars, researchers estimated values for fundamental parameters of the Milky Way. The distance from the sun to the galaxy’s center is 8,150 ± 150 parsecs (or 26,600 light-years), which is smaller than the value of 8,500 parsecs recommended decades ago by the International Astronomical Union.
They also find that the Milky Way is spinning at 236 kilometers per second, which is about eight times the speed at which Earth orbits the sun. The sun circles the Milky Way every 212 million years.
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