The Leo Triplet is a photogenic gathering of three barred spiral galaxies in Leo — Messier 65 (NGC 3623), Messier 66 (NGC 3627) and the edge-on Hamburger Galaxy (NGC 3628) — cataloged individually yet framed together within a single field of view. For astrophotographers this trio is a rewarding target because all three fit comfortably in the frame of a short focal-length telescope or a fast astrograph, offering contrasting galaxy shapes in one composition. Messier 66 shines at 8.92 mag with a surface brightness of 22.138 mag/arcsec², while the fainter NGC 3628 at 9.48 mag and a lower surface brightness of 23.2837 mag/arcsec² demands more integration time to reveal its dark dust lane and faint tidal tail. Long exposures under dark skies bring out the sweeping spiral arms of Messier 65 and Messier 66 alongside the sliver of NGC 3628, making the group a classic showcase image for deep-sky imagers.
Names and Catalog numbers
- Leo Triplet
- Leo Triplet
- M 65 (Messier 65) (member object: M 65)
- NGC 3623 (member object: M 65)
- UGC 6328 (member object: M 65)
- PGC 34612 (member object: M 65)
- M 66 (Messier 66) (member object: M 66)
- NGC 3627 (member object: M 66)
- UGC 6346 (member object: M 66)
- PGC 34695 (member object: M 66)
- Arp 16 (member object: M 66)
- Hamburger Galaxy (member object: NGC 3628)
- NGC 3628 (member object: NGC 3628)
- UGC 6350 (member object: NGC 3628)
- PGC 34697 (member object: NGC 3628)
Position and the cosmic neighborhood
The Leo Triplet lies in the constellation Leo, centered near right ascension 11h 17m and declination +13° 25′, high on the ecliptic-adjacent spring sky. Its three members are tightly clustered: Messier 65 (NGC 3623) sits at RA 11h 18m, Dec +13° 05′, Messier 66 (NGC 3627) close by at RA 11h 20m, Dec +12° 59′, and the Hamburger Galaxy (NGC 3628) just to the north at RA 11h 20m, Dec +13° 35′. Because all three fall within roughly a degree of one another, they are readily captured in a single wide-field frame, letting imagers record an interacting family of galaxies at distances of about 27.0, 23.9 and 38.8 million light-years respectively. This compact arrangement in a relatively star-poor region of Leo makes the group an ideal spring-season centerpiece for mid-northern latitudes.
Nice to Know
- All three galaxies — Messier 65, Messier 66 and the Hamburger Galaxy (NGC 3628) — are barred spirals, giving the field a striking variety of orientations from near face-on to fully edge-on.
- The Hamburger Galaxy (NGC 3628) presents an enormous apparent extent of 24′ × 4.8′ and a physical diameter of 276,000 light-years, its prominent dust lane splitting the edge-on disk in long-exposure images.
- Messier 65 (NGC 3623) spans 125,000 light-years across and stretches 16′ × 4.5′ on the sky, an elegant inclined spiral to pair with its neighbors.
- Messier 66 (NGC 3627), also cataloged as Arp 16, is the brightest member at 8.92 mag and measures 79,600 light-years in diameter, its asymmetric arms hinting at past gravitational interaction within the group.
