NGC 7793

NGC 7793 is a flocculent spiral galaxy in the southern constellation of Sculptor. It was discovered on July 14, 1826, by Scottish astronomer James Dunlop.^[7][8] The galaxy is located at a distance of 12.2^[4] million light years and is receding with a heliocentric radial velocity of 227 km/s.^[3] NGC 7793 is one of the five brightest galaxies within the Sculptor Group.^[6][5]

NGC 7793
Hubble Space Telescope image of the small bulge and spiral arms of NGC 7793
Observation data (J2000 epoch)
Constellation	Sculptor
Right ascension	23h 57m 49.753s[1]
Declination	−32° 35′ 27.71″[1]
Redshift	0.000749[2]
Heliocentric radial velocity	227 km/s[3]
Distance	12.2 Mly (3.7 Mpc)[4]
Group or cluster	Sculptor Group[5]
Apparent magnitude (V)	10.0[6]
Characteristics
Type	SA(s)d[2]
Mass	Stellar: 3.2×109 M☉
Size	~50,900 ly (15.61 kpc) (estimated)[2]
Apparent size (V)	9.3′ × 6.3′[6]
Other designations
ESO 349- G 012, IRAS 23552-3252, MCG -06-01-009, PGC 73049[2]

The morphological class of NGC 7793 is SA(s)d,^[2] indicating it is unbarred spiral galaxy (SA) with no inner ring structure (s) and the arms are loosely wound and disorganized (d). It is flocculent in appearance with a very small bulge and a star cluster at the nucleus.^[6] The galactic disk is inclined at an angle of 53.7° to the line of sight from the Earth. The visible profile is elliptical in form with an angular size of 9.3′ × 6.3′^[6] and a major axis aligned along a position angle of 99.3°.^[2] There are two nearby dwarf galaxy companions.^[9]

NGC 7793 hosts the ultra-luminous X-ray pulsar (ULXP) referred to as NGC 7793 P13 (previously believed to harbor a black hole), which consists of a 0.42-second pulsar in a 64-day orbit with a 18–23 solar mass B9Ia companion star.^[10]

Supernova

One supernova has been observed in NGC 7793. SN 2008bk (Type II-P, mag. 12.6) was discovered by Berto Monard (bio-it) on March 25, 2008.^[11][12][13] It reached apparent magnitude 12.5, making it the second-brightest supernova of 2008.^[14] The progenitor of this supernova was a red supergiant, observed only 547 days prior to the explosion.^[15]

Gallery

• 
  Visual and infrared image of NGC 7793
• 
  SN 2008bk before it exploded (left) and after the explosion (right)

See also

• List of NGC objects (7001–7840)
• NGC 300 – a similar spiral galaxy that is near NGC 7793
• NGC 2403 – a similar spiral galaxy