XMM-Newton and Chandra revise distance to Milky Way's outer spiral arms using gamma-ray burst echoes (esa.int)

• Three gamma-ray bursts produced X-ray echoes used for distance measurement.
• Outer arms found up to 10% more distant than previous estimates.
• Research published in Astronomy & Astrophysics on 29 June 2026.

"ESA's XMM-Newton and NASA's Chandra X-ray observatories have used light echoes from three gamma-ray bursts to directly measure the distance to the Milky Way's outer spiral arms. The results, published in Astronomy & Astrophysics, show that the Outer Scutum-Centaurus Arm and the Outer Arm are up to 10% farther away than previously estimated, while the Perseus Arm distance is confirmed."