Milky Way Outer Arms Stretch 10% Farther, Potentially Revising Galaxy Mass
Updated
Updated · Gizmodo · Jul 7
Milky Way Outer Arms Stretch 10% Farther, Potentially Revising Galaxy Mass
3 articles · Updated · Gizmodo · Jul 7
Summary
Astronomers found the Milky Way’s Outer and Outer Scutum-Centaurus arms sit about 10% farther away than previous estimates, a shift that could alter calculations of the galaxy’s size and mass.
Three gamma-ray bursts supplied the measurements: researchers used X-ray light echoes captured by NASA’s Chandra and ESA’s XMM-Newton to gauge dust-cloud distances through geometry rather than rotation-based models.
The team measured the Perseus, Outer and Outer Scutum-Centaurus arms, and estimated a dust cloud in the most distant arm is about 3,500 light-years wide, supporting that the result reflects the arm’s full thickness.
The finding matters because the Milky Way—about 100,000 light-years across—remains hard to map from inside its dusty disk, especially in its outer regions where standard methods grow less reliable.
Gamma-ray bursts could sharpen future distance estimates, but usable events are scarce: researchers said only a handful have been found through the Milky Way’s plane over the past 25 years.