Astronomy Picture of the Day . ... Credit: Ralf Muendlein (data acquisition), Wolfgang Kloehr (processing) Explanation: Big, beautiful spiral galaxy NGC 7331 is often touted as an analog to our own Milky Way . About 50 million light-years distant in the northern constellation Pegasus , NGC 7331 was recognized early on as a spiral nebula and is actually one of the brighter galaxies not included in Charles Messier's famous 18th century catalog. ... Publications with keywords: spiral galaxy . ...