Milky Way Arms Sit 10% Farther, Making Galaxy Larger and Lopsided
Updated
Updated · Livescience.com · Jul 9
Milky Way Arms Sit 10% Farther, Making Galaxy Larger and Lopsided
3 articles · Updated · Livescience.com · Jul 9
Summary
Two Milky Way spiral arms—the Outer and Scutum-Centaurus—appear about 10% farther from Earth than previous estimates, pushing parts of the galaxy several thousand light-years outward.
Gamma-ray burst X-ray echoes drove the revision: researchers used Chandra and XMM-Newton data from three bursts to gauge distances through gas clouds more directly than rotation-based models.
That shift could force updates to the Milky Way’s size and mass, now commonly put near 100,000 light-years across and about 1.5 trillion solar masses.
The new map also hints the galaxy is less symmetrical than assumed, because the Perseus arm did not show the same outward shift and the revised arms make the Milky Way look more uneven.
Researchers say the picture is still incomplete, since only a handful of usable gamma-ray bursts have been found in 25 years and more are needed to map the remaining arms.