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Astronomers Map Milky Way Spiral Arm Distances With X-Ray Rings
A team measured distances to dust clouds in the Milky Way using X-ray data from NASA’s Chandra and ESA’s XMM-Newton telescopes. The geometric method relied on rings created by gamma-ray bursts reflecting off the clouds. Results indicate the most distant arm dust cloud spans about 3,500 light-years.
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Astronomers measured distances to dust clouds in the Milky Way’s spiral arms by analyzing X-ray rings produced when gamma-ray bursts from distant galaxies reflected off the clouds. The data came from NASA’s Chandra X-ray telescope and ESA’s XMM-Newton telescope. Beatrice Vaia, the Italian PhD student who led the study, said the approach relies only on geometry.
“This is a very direct way — relying only on geometry — to precisely measure distances to the Milky Way’s spiral arms,” she stated. She added that most other methods depend on assumptions about galactic rotation that grow uncertain farther from the center. The dust cloud in the most distant arm was estimated at about 3,500 light-years wide.
Earth sits inside one of the galaxy’s spiral arms, a position that has long complicated mapping efforts known for at least a century. Ilaria Fornasiero, a PhD student and co-author, said small revisions matter because distances underpin basic models of the galaxy.
“For example, this could mean that astronomers have to revise estimates of the mass of the galaxy, because that affects how wide the arms stretch,” she stated.
Suitable gamma-ray bursts remain rare. Researchers have identified only a handful bright enough and positioned correctly over the past 25 years. Co-author Andrea Tiengo said the team will continue searching for additional events.
