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Looking at the stars at night, it is always so intoxicating. People living in cities do not hesitate to be far away and are willing to go to the suburbs to watch the stars and the moon. Especially when people look at the dazzling Galaxy , they always feel that humans are insignificant and the vastness of the universe. So, how big is galaxy ? This has always been a difficult problem for scientists to observe.
However, there have been new breakthroughs in the measurement of the mass of the Milky Way recently. Using data from my country's Guo Shoujing Telescope (LAMOST) and the ESA's Gaia satellite, an international research team accurately measured the mass of the Milky Way that was about 550 billion times the mass of the sun. The results are nearly half smaller than the average measured by other international teams (about 1000 billion times the mass of the sun) and nearly double the accuracy. Recently, this research result was published in the British "Royal Astronomical Society Monthly".
researchers said in a research article that they proposed a study on the effect of GSE on the halo density shape of the Milky Way star, using 11,624 K superstars from the LAMOST survey. Each star is assigned the probability of becoming a GSE member through the Gaussian hybrid model according to its spherical velocity and metal quantity.
It is reported that according to the probability obtained, the star halo is divided into two parts, one of which is composed of GSE members and defined as the GSE related halo, and the other part is called the GSE removed halo. Using a non-parametric method, the radial number density distribution of two star halos can be described by a single power law with variable flattened q. The index α of the GSE-related halo is 4.92 ± 0.12, and the index of the GSE-removing halo is 4.25 ± 0.14. The two star halos are vertically flat at smaller radii, but become more spherical at larger radii.
"We found that the vertical flatness of the GSE-related halo is smaller compared to the GSE-removed halo, with the q difference between the two star halos ranging from 0.07 to 0.15. However, after considering the deviation, it was considered to be 0.08 for most of the radius. Finally, we compared the results with two galaxy analogs that experienced major mergers in the TNG50 simulation. The study of these two analogs also showed that the ellipticity of the main star halos associated with the merge was smaller than that of the main merge-removed star halos," the researchers said.
researchers pointed out in an earlier interview with the media that the latest research results show that the Milky Way may be "slimmer" than everyone thinks. This means that there are much less dark matter in the Milky Way that does not glow but produces gravity than originally estimated. This further supports the conjecture of Hans-Walter Ricks, director of the Max Planck Institute for Astronomy, that the smaller mass of the Milky Way means that the Milky Way forces satellite galaxies to rotate around them, so the large, small Magellan cloud may not be the satellite galaxy of the Milky Way, but just a "passerby" who happens to be near the Milky Way.
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Author: Mai Wanhua
Editor: Zhao Dina
Review: Gong Zimo
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