XMM-Newton helps revise distances to outer spiral arms of the Milky Way (aanda.org)

• Precise distance measurement to three spiral arms using X-ray scattering rings
• New rings discovered in GRB 160623A at 6.91 and 9.9 kpc
• Outer Scutum-Centaurus arm measured at 19.0 ± 0.2 kpc, ten times more precise than before
• Deviations from kinematic models of galactic rotation found

"Using X-ray dust scattering rings around gamma-ray bursts, researchers measured precise distances to the Milky Way's outer spiral arms. Analysis of XMM-Newton and Chandra data from GRBs 031203, 160623A, and 221009A provides direct geometric distances to dust clouds in the Perseus, Outer, and Outer Scutum-Centaurus arms. New rings were discovered at 6.91 and 9.9 kpc. The measurements show systematic deviations from kinematic models based on the galactic rotation curve. The Outer Scutum-Centaurus arm lies at 19.0 ± 0.2 kpc, significantly more precise than previous measurements."