A Trigonometric Parallax of Sgr B2

TL;DR

This paper reports a precise measurement of the distance to the Galactic center using water maser observations in Sgr B2, providing key data for understanding Galactic structure.

Contribution

It presents the first trigonometric parallax measurement of Sgr B2, refining the distance to the Galactic center with high accuracy.

Findings

Distance to Galactic center: 7.9 kpc

Sgr B2 is about 0.13 kpc closer than the Galactic center

Proper motion data supports low-eccentricity orbit hypothesis

Abstract

We have measured the positions of water masers in Sgr B2, a massive star forming region in the Galactic center, relative to an extragalactic radio source with the Very Long Baseline Array. The positions measured at 12 epochs over a time span of one year yield the trigonometric parallax of Sgr B2 and hence a distance to the Galactic center of Ro=7.9 (+0.8/-0.7) kpc. The proper motion of Sgr B2 relative to Sgr A* suggests that Sgr B2 is about 0.13 kpc nearer than the Galactic center, assuming a low-eccentricity Galactic orbit.