NGC 45

NGC 45
NGC 45 by DECam
Observation data (2000.0 epoch)
Constellation	Cetus
Right ascension	00° 14′ 03.989″[1]
Declination	–23h 10m 55.53s[1]
Redshift	0.001558[2]
Heliocentric radial velocity	466 km/s[3]
Distance	21.7 Mly (6.64 Mpc)[4]
Apparent magnitude (V)	10.73±0.03[5]
Apparent magnitude (B)	11.21±0.03[5]
Characteristics
Type	SA(s)dm[6]
Mass/Light ratio	[7] M☉/L☉
Apparent size (V)	7.41′ × 5.13'
Other designations
UGCA 4, LEDA 930, MCG -04-01-21, PGC 930[8]

NGC 45 is a low surface brightness^[7] spiral galaxy in the equatorial constellation of Cetus. It was discovered on 11 November 1835 by the English astronomer John Herschel.^[9] The galaxy is located at a distance of 22^[4] million light years and is receding with a heliocentric radial velocity of 466 km/s.^[3] It is located in the vicinity of the Sculptor Group, but is most likely a background galaxy.^[7]

The morphological class of NGC 45 is SA(s)dm,^[6] indicating this is a spiral galaxy with no prominent inner bar (SA) or ring (s) feature. There is no central bulge to speak of.^[7] The galactic plane is inclined at an angle of 55°±5° to the line of sight from the Earth, with the major axis of the elliptical profile being aligned along a position angle of 145°±5°.^[7] Star formation is proceeding at a modest rate of ~0.20 M_☉·yr⁻¹.^[6]

Unlike the Milky Way, NGC 45 has no clearly defined spiral arms, and its center bar nucleus is also very small and distorted. NGC 45 thus does not have a galactic habitable zone.^[10][11][12] For the Milky Way, the galactic habitable zone is commonly believed to be an annulus with an outer radius of about 10 kiloparsecs and an inner radius close to the Galactic Center, both of which lack hard boundaries.^[11]

Two astronomical transients have been observed in NGC 45. On 22 May 2018 a luminous red nova was detected and subsequently labeled AT 2018bwo (type LRN, mag. 16.4).^[13] Luminous red novae are thought to be the result of stars merging. The progenitor of AT 2018bwo was a yellow supergiant star.^[14] A few months later, on 3 November 2018, a luminous blue variable was discovered and designated AT 2018htr (type LBV, mag. 17.5).^[15]

• 
  Galex (ultraviolet) view of NGC 45
• 
  Hubble mosaic of NGC 45

• List of NGC objects (1–1000)

• Revised NGC Data for NGC 45
• Media related to NGC 45 at Wikimedia Commons
• NGC 45 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images