YNU researcher: Milky Way almost doubles previous estimates

A researcher from Yunnan University, or YNU – located in Kunming, capital of Southwest China's Yunnan province – has said that the size of the famed Milky Way galaxy is almost twice the previous estimates.

Recently, Chinese scientists used data from the APOGEE near-infrared stellar spectroscopy survey to reconstruct for the first time the complete radial density distribution of stars in the Milky Way from the inside out.

They reported that the direct measurement results indicated that the Milky Way was much larger than previously assumed.

The related research findings were published in the international authoritative academic journal Nature Astronomy.

Lian Jianhui, the first author of the paper and an associate professor at the South-Western Institute for Astronomy Research of Yunnan University, explained that based on the new stellar surface density distribution, new estimates were applied.

The research team found that the half-light radius of the Milky Way – the radius containing half of the galaxy's total luminosity – was almost twice the previously estimated size of about 19,000 light-years and was consistent with the radius of nearby galaxies of a similar mass, indicating that the Milky Way was a typical disk galaxy in terms of its size.

The researchers conducted a comprehensive analysis of the inhomogeneity, dust and stellar properties observed by the APOGEE survey, the first large-scale near-infrared stellar spectroscopy survey.

They then systematically reconstructed the true and complete surface density distribution of the stars of different ages from the bulge to the outer disk of the Milky Way.

The results, they affirmed, showed that the disk structure of the Milky Way followed a classic exponential distribution in the outer disk region.

However, in the inner disk region, the stellar density remained almost flat, significantly deviating from the exponential distribution of the outer disk.

Lian stated that the latest research opened new dimensions for measuring the overall physical properties of the Milky Way and conducting cross-comparison studies with extragalactic galaxies, which would have a significant impact on related studies of the Milky Way.