Our galactic neighborhood might be more expansive than thought. Rather than being stuck in a backwater galactic community, our solar system sits along a major spiral arm of the Milky Way, researchers say September 28 in Science Advances.
Astronomers suspected that our arm — the Orion Arm — was just a bridge connecting two bands of stars and gas: the Sagittarius and Perseus arms that wrap around the galaxy. Ye Xu of Purple Mountain Observatory in Nanjing, China, and colleagues measured distances to about two dozen stellar nurseries and found that they— and the sun — are scattered along an arm over 20,000 light-years long that parallels the two neighboring arms. This arc of a presumably larger spiral arm is comparable in length to the visible portions of the Sagittarius and Perseus arms.
Our view of the Milky Way is blocked by interstellar gas and dust, so the galaxy’s structure must be inferred through measurements like these and by comparisons with other galaxies.
Y. Xu et al. The local spiral structure of the Milky Way. Science Advances. Published online September 28, 2016. doi: 10.1126/sciadv.1600878.