M101 — Pinwheel Galaxy
A large face-on spiral galaxy in Ursa Major, its diffuse arms dotted with HII regions, captured over several nights.
View photos ↓- Object type
- Spiral galaxy
- Constellation
- Ursa Major
- Designation
- M101 (NGC 5457)
- Distance
- ≈ 21 million light-years
- Apparent magnitude
- 7.9
- Apparent size
- ≈ 28.8 x 26.9 arcmin
- Best season
- Spring (best visibility March-May)
The Pinwheel Galaxy (M101, NGC 5457) is a large, face-on spiral galaxy in the constellation Ursa Major. Its widely open, asymmetric arms, dotted with numerous HII regions of active star formation, give it an irregular structure likely shaped by gravitational interactions with its satellite galaxies.
Despite an apparent size close to that of the full Moon, its low surface brightness makes it a demanding target under light-polluted skies, requiring a substantial amount of integration time to bring out its spiral arms.
This target was revisited over five nights spread between July and August 2026 with the Seestar S30 Pro mounted in equatorial mode on the EQ3, fitted with its light pollution filter: 552 sub-exposures of 10 and 30 seconds, for about 4h23 of total integration, stacked and processed in PixInsight.
