NGC 2403

NGC 2403
A Hubble Space Telescope (HST), and Subaru image of NGC 2403. NGC 2404 is visible
Observation data (J2000 epoch)
Constellation	Camelopardalis
Right ascension	07h 36m 51.298s [1]
Declination	+65° 36′ 09.662″ [1]
Redshift	0.000445 [1]
Heliocentric radial velocity	133 ± 0 km/s [1]
Distance	9.65 Mly (2.96 Mpc) [2]
Apparent magnitude  (V)	8.9 [1]
Characteristics
Type	SAB(s)cd [1]
Size	~90,300  ly (27.69  kpc) (estimated) [1]
Apparent size  (V)	21.9′ × 12.3′ [1]
Other designations
Caldwell 7, IRAS 07321+6543, UGC 3918, PGC 21396, CGCG 309-040 [1]

NGC 2403 (also known as Caldwell 7) is an intermediate spiral galaxy in the constellation Camelopardalis. It is an outlying member of the M81 Group, ^[3] and is approximately 8 million light-years distant.

Observation history

The galaxy was discovered by German-British astronomer William Herschel on 1 November 1788. ^[4] Edwin Hubble detected Cepheid variables in NGC 2403 using the Hale Telescope, making it the first galaxy beyond the Local Group within which a Cepheid was discovered. ^[3] By 1963, 59 variables had been found in NGC 2403, of which 17 were eventually confirmed as Cepheids, with periods between 20 and 87 days. As late as 1950 Hubble was using a distance of just under 2 million light years for the galaxy's distance, but by 1968 the analysis of the Cepheids increased this by almost a factor of five, to within 0.2 magnitudes of the current value.

Characteristics

A Galaxy of Birth and Death

NGC 2403 bears a similarity to M33, containing numerous star-forming H II regions, but being a little bit larger at approximately 90,000 light-years in diameter compared to the 61,100 light-year diameter of M33. ^[5] The northern spiral arm connects it to the star forming region NGC 2404. ^[3] NGC 2403 can be observed using 10×50 binoculars. ^[3] NGC 2404 is 940 light-years in diameter, making it one of the largest known H II regions. This H II region represents striking similarity with NGC 604 in M33, both in size and location in galaxy.

Supernovae and supernovae imposters

There have been four reported astronomical transients in the galaxy:

• SN 1954J was first noticed by Gustav Tammann and Allan Sandage as a "bright blue irregular variable" star, which they named V12. They noted it underwent a major outburst on 2/3 November 1954, which attained a magnitude of 16 at its brightest. ^[6] In 1972, Fritz Zwicky classified this event as a Type V supernova. ^[7] It was later determined to be a supernova imposter: a highly luminous, very massive eruptive star, surrounded by a dusty nebula, similar to the 1843 Great Eruption of η Carinae in the Milky Way. ^[8]
• SN 2002 kg was discovered by LOTOSS (Lick Observatory and Tenagra Observatory Supernova Searches) on 26 October 2002 and initially classified as a Type IIn, or possibly the outburst of a luminous blue variable. ^[9] On 24 August 2021, it was reclassified as a Gap transient. ^[10]
• SN 2004dj (Type II-P, mag. 11.2) was discovered by Kōichi Itagaki on 31 July 2004. ^{[11] [12]} At the time of its discovery, it was the nearest and brightest supernova observed in the 21st century, and is now listed as the brightest supernova of 2004. ^[13]
• AT 2016ccd, initially designated as SNhunt225, is a luminous blue variable, first discovered by Catalina Real-time Transient Survey (CRTS) and Stan Howerton in December 2013. Outbursts from this star have been observed as recently as November 2021. ^{[14] [15]}

Companions

NGC 2403 has two known companions. One is the relatively massive dwarf galaxy DDO 44. It is currently being disrupted by NGC 2403, as evidenced by a tidal stream extending 82  kly (25  kpc ) on both sides of DDO 44. DDO 44 is approaching NGC 2403 at a distance much closer than typical for dwarf galaxy interactions. It currently has a V-band absolute magnitude of −12.9, but its progenitor was even more luminous. ^[2]

The other known companion is officially named MADCASH J074238+652501-dw, although it is nicknamed MADCASH-1. The name refers to the MADCASH (Magellanic Analog Dwarf Companions and Stellar Halos) project. MADCASH-1 is similar to typical dwarf spheroidal galaxies in the Local Group; it is quite faint, with an absolute V-band magnitude of −7.81, and has only an ancient, metal-poor population of red giant stars. ^[16]

See also

• Triangulum Galaxy - looks very similar to NGC 2403.
• List of NGC objects (2001–3000)

References

1. "Results for object NGC 2403". NASA/IPAC Extragalactic Database. NASA and Caltech . Retrieved 2006-11-21.
2. Carlin, Jeffrey L.; Garling, Christopher T.; Peter, Annika H. G.; Crnojević, Denija; Forbes, Duncan A.; Hargis, Jonathan R.; Mutlu-Pakdil, Burçin; Pucha, Ragadeepika; Romanowsky, Aaron J.; Sand, David J.; Spekkens, Kristine; Strader, Jay; Willman, Beth (2019). "Tidal Destruction in a Low-mass Galaxy Environment: The Discovery of Tidal Tails around DDO 44". The Astrophysical Journal. 886 (2): 109. arXiv: 1906.08260 . Bibcode:2019ApJ...886..109C. doi: 10.3847/1538-4357/ab4c32 . S2CID   195218404.
3. Kepple, George Robert; Glen W. Sanner (1998). The Night Sky Observer's Guide. Vol. 1. Willmann-Bell, Inc. p. 73. ISBN   978-0-943396-58-3.
4. Seligman, Courtney. "New General Catalogue Objects: NGC 2403". Celestial Atlas. Retrieved 21 May 2025.
5. Ho, Luis C.; Filippenko, Alexei V.; Sargent, Wallace L. W. (October 1997). "A Search for "Dwarf" Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies". Astrophysical Journal Supplement. 112 (2): 315–390. arXiv: astro-ph/9704107 . Bibcode:1997ApJS..112..315H. doi:10.1086/313041. S2CID   17086638.
6. Tammann, G. A.; Sandage, Allan (1968). "The Stellar Content and Distance of the Galaxy NGC 2403 IN the M81 Group". The Astrophysical Journal. 151: 825. Bibcode:1968ApJ...151..825T. doi: 10.1086/149487 .
7. Kowal, C. T.; Sargent, W. L. W.; Searle, L.; Zwicky, F. (1972). "The 1971 Palomar Supernova Search". Publications of the Astronomical Society of the Pacific. 84 (502): 844. Bibcode:1972PASP...84..844K. doi: 10.1086/129392 .
8. Van Dyk, Schuyler D.; Filippenko, Alexei V.; Chornock, Ryan; Li, Weidong; Challis, Peter M. (2005). "Supernova 1954J (Variable 12) in NGC 2403 Unmasked". Publications of the Astronomical Society of the Pacific. 117 (832): 553–562. arXiv: astro-ph/0503324 . Bibcode:2005PASP..117..553V. doi:10.1086/430238.
9. Schwartz, M.; Li, W.; Filippenko, A. V.; Chornock, R. (2003-01-01). "Supernova 2002kg in NGC 2403". International Astronomical Union Circular. 8051: 1. Bibcode:2003IAUC.8051....1S.
10. "SN 2002 kg". Transient Name Server. IAU . Retrieved 14 August 2024.
11. Nakano, S.; Itagaki, K.; Bouma, R. J.; Lehky, M.; Hornoch, K. (2004-08-01). "Supernova 2004dj in NGC 2403". International Astronomical Union Circular (8377): 1. Bibcode:2004IAUC.8377....1N.
12. "SN 2004dj". Transient Name Server. IAU . Retrieved 14 August 2024.
13. Bishop, David. "Bright Supernovae - 2004". Rochester Astronomy. Retrieved 21 August 2025.
14. Bishop, David (9 November 2021). "LBV AT2016ccd in NGC 2403". Rochester Astronomy. Retrieved 31 August 2024.
15. "AT 2016ccd". Transient Name Server. IAU . Retrieved 31 August 2024.
16. Carlin, Jeffrey L.; Mutlu-Pakdil, Burçin; Crnojević, Denija; Garling, Christopher T.; Karunakaran, Ananthan; Peter, Annika H. G.; Tollerud, Erik; Forbes, Duncan A.; Hargis, Jonathan R.; Lim, Sungsoon; Romanowsky, Aaron J.; Sand, David J.; Spekkens, Kristine; Strader, Jay (2021). "Hubble Space Telescope Observations of Two Faint Dwarf Satellites of Nearby LMC Analogs from MADCASH". The Astrophysical Journal. 909 (2): 211. arXiv: 2012.09174 . Bibcode:2021ApJ...909..211C. doi: 10.3847/1538-4357/abe040 . S2CID   229297953.

External links

• Spiral Galaxy NGC 2403 at the astro-photography site of Mr. Takayuki Yoshida
• NGC 2403 at ESA/Hubble
• NGC 2403 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images
• NASA Astronomy Picture of the Day: NGC 2403 (19 February 2016)
• SEDS – NGC 2403