Chinese scientists accurately measured the Milky Way's "weight"

The latest "weight" of the Milky Way is here! On the 20th, the reporter learned from the National Astronomical Observatory of the Chinese Academy of Sciences that based on the observation data of my country's Guo Shoujing Telescope (LAMOST) and the APOGEE survey in the United States, Chinese astronomers accurately measured the movement speed of stars within 16,000 to 81,000 light-years from the center of the Milky Way, and estimated that the "weight" of the Milky Way is about 805 billion solar masses. The relevant research results were published online in the Astrophysical Journal.

Measuring the mass of the Milky Way is a challenging problem. There is no existing scale that can weigh this galaxy-sized "fat guy." Measuring the rotation curve of the Milky Way, that is, the movement speed of stars at different distances from the center of the Milky Way, is one of the common methods currently used by astronomers to measure the mass of the Milky Way.

"However, it is not easy to estimate the mass of the Milky Way using its rotation curve. It requires information on a number of iconic celestial bodies that are far away from the center of the Milky Way, such as the precise distance of the celestial bodies from the center of the Milky Way, their proper velocity and radial velocity, etc." said Huang Yang, associate professor at the University of Chinese Academy of Sciences and corresponding author of the paper.

This time, researchers collected spectral data of more than 250,000 bright red giant stars in the Milky Way from LAMOST and APOGEE survey data. "These spectral data provide accurate information on stellar atmospheric parameters, motion speed, chemical element abundance and other parameters, providing good conditions for accurately measuring the rotation curve of the Milky Way," said Huang Yang.

Afterwards, the researchers selected about 54,000 Milky Way thin disk stars from the more than 250,000 bright red giants, which have information on radial velocity, proper motion velocity and spectroscopic distance. "On this basis, we constructed the Milky Way rotation curve within the range of 16,000 to 81,000 light-years from the center of the Milky Way." Huang Yang said that based on the rotation curve, the researchers further constructed a mass model of the Milky Way and estimated that the mass of the Milky Way is about 805 billion solar masses.

Huang Yang said that this study has drawn the most accurate rotation curve of the Milky Way so far, which provides crucial constraints for measuring basic physical quantities such as the total mass of the Milky Way and the density of dark matter near the sun. It is of great significance for searching for dark matter particles and understanding the distribution of dark matter in the Milky Way. The reviewers of the paper also highly praised the results: "This is the best measurement of the rotation curve of the Milky Way so far."

Science and Technology Daily reporter Lu Chengkuan