The Milky Way’s Unusual Twin in Pegasus

The magnificent spiral galaxy NGC 7331, located approximately 40 million light-years away in the constellation Pegasus, is the brightest and closest galaxy in the visual galaxy group that bears its name, the NGC 7331 Group. Revealed in the details of this image are populations of hot stars and dark dust lanes winding throughout the spiral arms. Also known as Caldwell 30, this galaxy is often thought of as a twin to the Milky Way owing to its similar size and spiral structure. However, there are a couple of features of its core that set it apart from our home galaxy. For instance, astronomers have found evidence that the Milky Way has a central bar of stars and dust cutting through its center, a feature common to many spiral galaxies. But NGC 7331 lacks this feature. Additionally, NGC 7331’s central bulge rotates in the opposite direction to its galactic disk — unusual behavior compared to other galaxies and different from what we observe in the Milky Way.

This image was taken by Gemini North, one half of the International Gemini Observatory, supported in part by the U.S. National Science Foundation and operated by NSF NOIRLab. You can find other views of NGC 7331 captured at Kitt Peak National Observatory, a Program of NSF NOIRLab, in 2014 and 1975 in the NOIRLab Image archive.