NGC 251

NGC 251 is a spiral galaxy in the constellation of Pisces. Its velocity with respect to the cosmic microwave background for is 4,224±23 km/s, which corresponds to a Hubble distance of 203.2 ± 14.3 Mly (62.30 ± 4.37 Mpc).^[2] Additionally, six non redshift measurements give a distance of 205.32 ± 5.54 Mly (62.950 ± 1.699 Mpc).^[4] It was discovered on October 15, 1784, by German-British astronomer William Herschel.^[5]

NGC 251
SDSS image of NGC 251
Observation data (J2000 epoch)
Constellation	Pisces
Right ascension	00h 47m 54.0517s[1]
Declination	+19° 35′ 48.788″[1]
Redshift	0.015184[2]
Heliocentric radial velocity	4556 km/s[2]
Distance	204.36 ± 12.64 Mly (62.657 ± 3.876 Mpc)[2]
Apparent magnitude (B)	14.6[3]
Characteristics
Type	Sc[2]
Size	149,300 ly (45,780 pc)[2][note 1]
Apparent size (V)	2.4′ × 1.9′[2]
Other designations
KPG 015B, UGC 490, PGC 2806, CGCG 458-005[3]

According to I.D. Karachentsev, NGC 251 forms an isolated galaxy pair with UGC 477.^[6]

One supernova has been observed in NGC 251: SN 2023rky (type II, mag. 18.6) was discovered by the Zwicky Transient Facility on 6 September 2023.^[7]

Notes

1. POSS1 103a-O values used.

See also

• List of NGC objects (1–1000)