Whirlpool Galaxy
The Whirlpool Galaxy, also known as Messier 51a (M51a) or NGC 5194, is an interacting grand-design spiral galaxy with a Seyfert 2 active galactic nucleus. It lies in the constellation Canes Venatici, and was the first galaxy to be classified as a spiral galaxy. It is 32 million light-years away and 109,000 ly (33,280 pc) in diameter.
| Whirlpool Galaxy | |
|---|---|
Whirlpool Galaxy (M51a), as taken by European Space Agency, the smaller object in the upper right is NGC 5195 (M51b) (NASA/ESA) | |
| Observation data (J2000.0 epoch) | |
| Constellation | Canes Venatici |
| Right ascension | 13h 29m 52.7s |
| Declination | +47° 11′ 43″ |
| Redshift | 0.001534±0.000007 |
| Distance | 9.76 ± 0.68 Mpc (31.83 ± 2.218 Mly)h−1 0.6774 (Comoving) 9.198 Mpc (30 Mly)h−1 0.6774 (Light-travel) |
| Apparent magnitude (V) | 8.4 |
| Characteristics | |
| Type | SA(s)bc pec |
| Size | 23.58 kpc (76.9 kly) (diameter; 25.0 mag/arcsec2 B-band isophote) |
| Apparent size (V) | 11.2′ × 6.9′ |
| Notable features | Interacting with NGC 5195 |
| Other designations | |
| Question Mark Galaxy, Rosse's Galaxy, M51a, NGC 5194, UGC 8493, PGC 47404, VV 001a, VV 403, Arp 85, GC 3572 | |
The galaxy and its companion, NGC 5195, are easily observed by amateur astronomers, and the two galaxies may be seen with binoculars. The Whirlpool Galaxy has been extensively observed by professional astronomers, who study it and its pair with NGC 5195 to understand galaxy structure (particularly structure associated with the spiral arms) and galaxy interactions. Its pair with NGC 5195 is among the most famous and relatively close interacting systems, and thus is a favorite subject of galaxy interaction models.