The Pinwheel Galaxy (M101)

M101 is a large face-on spiral galaxy in Ursa Major — its sweeping arms traced with bright star-forming regions and dark dust lanes, presenting one of the most detailed spiral structures visible from Earth.

Messier 101 lies around 21 million light-years away in Ursa Major and is one of the largest known spiral galaxies, spanning roughly 170,000 light-years — nearly twice the diameter of the Milky Way. Seen almost perfectly face-on, its spiral structure is fully exposed, with the arms studded by HII regions — glowing pink clouds where new stars are forming.

The face-on orientation that makes M101 so visually striking also makes it a low surface-brightness challenge. The outer arms in particular are faint, and pulling them out without introducing noise requires significant integration time.

The background field around M101 is rich with distant background galaxies — a reminder of how much is out there beyond our immediate cosmic neighbourhood. Several are bright enough to be worth noting in the final image.