A Trigonometric Parallax of Sgr B2

• Reid, M. J.
;
• Menten, K. M.
;
• Zheng, X. W.
;
• Brunthaler, A.
;
• Xu, Y.

Abstract

We have measured the positions of H₂O 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 R ₀ = 7.9^+0.8 _-0.7 kpc. The proper motion of Sgr B2 relative to Sgr A* suggests that Sgr B2 is ≈0.13 kpc nearer than the Galactic center, assuming a low-eccentricity Galactic orbit.