NGC 3998
| NGC 3998 | |
|---|---|
SDSS image of NGC 3998 | |
| Observation data (J2000 epoch) | |
| Constellation | Ursa Major |
| Right ascension | 11h 57m 56.1333s |
| Declination | +55° 27′ 12.922″ |
| Redshift | 0.003401 |
| Heliocentric radial velocity | 1020 ± 0 km/s |
| Distance | 45 Mly (13.7 Mpc) |
| Group or cluster | NGC 3631 group (LGG 241) |
| Apparent magnitude (V) | 12.10 |
| Apparent magnitude (B) | 11.64 |
| Characteristics | |
| Type | SA00(r): |
| Size | ~60,700 ly (18.61 kpc) (estimated) |
| Apparent size (V) | 2.7′ × 2.3′ |
| Other designations | |
| HOLM 310A, IRAS F11553+5543, UGC 6946, MCG +09-20-046, PGC 37642, CGCG 269-025 | |
NGC 3998 is a lenticular galaxy located in the constellation Ursa Major. It was discovered on April 14, 1789, by German-British astronomer William Herschel. At a distance of 45 million light-years (13.7 megaparsecs), it is located relatively nearby, making it a well-studied object.
In Gérard de Vaucouleurs' atlas of galaxy morphological types, NGC 3998 has a classification of SA00(r):, meaning it is unbarred and has an internal ring. It is classified as a LINER-type galaxy. As an early-type galaxy, NGC 3998's stars are relatively old and reddish in color, but its nuclear region may still have signs of star formation with stars less than 10 million years old. The galaxy's shape is very round, and also oblate.