Solar system sits within major spiral arm of Milky Way

milky way

Our solar system lives in a major spiral arm of the Milky Way, a new study suggests. This view looking toward the center of the galaxy was taken at the ESO 3.6-meter telescope in the Chilean Atacama Desert.

S. Brunier/ESO

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.

Star-forming regions (blue) trace out the Orion spiral arm where the sun (red circle) lives. Stellar nurseries along the neighboring Perseus and Sagittarius arms are shown in black and magenta; the center of the galaxy is marked with a red star. Y. Xu et al/Science Advances 2016

Christopher Crockett is an Associate News Editor. He was formerly the astronomy writer from 2014 to 2017, and he has a Ph.D. in astronomy from the University of California, Los Angeles.

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