NGC 3646

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NGC 3646
NGC3646 - SDSS DR14.jpg
NGC 3646 in the Sloan Digital Sky Survey
Observation data
Constellation Leo
Right ascension 11h 21m 43s
Declination +20° 10′ 10″
Redshift 0.01416 +/- 0.00001
Apparent magnitude  (V)11.13
Apparent magnitude  (B)11.78

NGC 3646 is a galaxy in the Leo constellation that has variously been described as "a strange spiral galaxy" of morphological classication Sc [1] or SAa, [2] or as "a ring-shaped galaxy". [3] [4]

NGC 3646 has a structure consisting of three parts: an inner hub, a rapidly rotating spiral, and an irregular outer ring surrounding the spiral with an angular feature at one point of the ring. [3] Although estimates vary for its distance, [3] [2] the NASA/IPAC Extragalactic Database lists its distance as 67.49 megaparsecs (220.1 Mly), ±4.74 megaparsecs (15.5 Mly). [4]

Burbidge et al. estimated that their measurements of motion in the outer ring were not consistent with stable circular orbits. [1] Afanas'ev et al. argue that this conclusion was erroneous, based on incorrect measurements. Instead, they find a galaxy rotation curve that "places the galaxy among the most rapidly rotating and massive systems", [3] "one of the largest and most luminous spirals in the local universe". [2]

NGC 3649 from the Sloan Digital Sky Survey NGC3649 - SDSS DR14.jpg
NGC 3649 from the Sloan Digital Sky Survey

NGC 3646 forms an isolated pair with a smaller companion galaxy, NGC 3649. [3] The high rate of star formation in NGC 3646, the low rate in its companion, and the unusual shape of the outer ring in NGC 3646 may have resulted from interactions between these two galaxies. [2]

Two supernovae have been seen in NGC 3646: SN 1989N, [5] [6] [7] and SN 1999cd. [8] [9]

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<span class="mw-page-title-main">NGC 6118</span> Galaxy in the constellation Serpens

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<span class="mw-page-title-main">NGC 3021</span> Galaxy in the constellation Leo Minor

NGC 3021 is a spiral galaxy in the northern constellation of Leo Minor. It is about 93 million light-years away from Earth, and is receding with a heliocentric radial velocity of 1,537±4 km/s. This galaxy was discovered December 7, 1785 by Anglo-German astronomer William Herschel. The morphological classification of NGC 3021 is SA(rs)bc, which indicates a spiral galaxy with no central bar (SA), an incomplete inner ring structure (rs), and moderate to loosely wound spiral arms (bc).

<span class="mw-page-title-main">NGC 132</span> Spiral galaxy in the constellation Cetus

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<span class="mw-page-title-main">NGC 180</span> Galaxy in the constellation Pisces

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<span class="mw-page-title-main">NGC 182</span> Spiral galaxy in the constellation Pisces

NGC 182 is a spiral galaxy with a ring structure, located in the constellation Pisces. It was discovered on December 25, 1790 by William Herschel.

<span class="mw-page-title-main">NGC 214</span> Galaxy in the constellation Andromeda

NGC 214 is a spiral galaxy in the northern constellation of Andromeda, located at a distance of 194 megalight-years from the Milky Way. It was discovered on September 10, 1784 by William Herschel. The shape of this galaxy is given by its morphological classification of SABbc, which indicates a weak bar-like structure (SAB) at the core and moderate to loosely-wound spiral arms (bc).

<span class="mw-page-title-main">NGC 3313</span> Galaxy in the constellation Hydra

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<span class="mw-page-title-main">NGC 3294</span> Galaxy in the constellation Leo Minor

NGC 3294 is a spiral galaxy in the constellation Leo Minor. It was discovered by William Herschel on Mar 17, 1787. It is a member of the Leo II Groups, a series of galaxies and galaxy clusters strung out from the right edge of the Virgo Supercluster. The galaxy is located at a distance of 98 million light years and is receding with a heliocentric radial velocity of 1,586 km/s. The morphological class of NGC 3294 is SA(rs)bc, which means this is a spiral galaxy with no central bar (SA), an incomplete inner ring structure (rs), and moderately wound spiral arms (bc).

References

  1. 1 2 Burbidge, E. Margaret; Burbidge, G. R.; Prendergast, K. H. (1961), "Motions in NGC 3646, a strange spiral galaxy", Astrophysical Journal, 134: 237–243, Bibcode:1961ApJ...134..237B, doi:10.1086/147145
  2. 1 2 3 4 Smith, Beverly J.; Zaragoza-Cardiel, Javier; Struck, Curtis; Olmsted, Susan; Jones, Keith (February 2016), "A comparative study of knots of star formation in interacting versus spiral galaxies", The Astronomical Journal, 151 (3): 63, arXiv: 1601.02664 , Bibcode:2016AJ....151...63S, doi: 10.3847/0004-6256/151/3/63
  3. 1 2 3 4 5 Afanas'ev, A. V.; Burenkov, A. N.; Zasov, A. V.; Sil'chenko, O. K. (December 1991), "The rotation of inner parts of spiral galaxies, NGC 497, 895, 972 and 3646.", Astronomicheskii Zhurnal, 68: 1134–1149, Bibcode:1991AZh....68.1134A
  4. 1 2 "Results for object NGC 3646", NASA/IPAC Extragalactic Database , retrieved 2023-07-29
  5. ↑ Mikolajczak, C.; Helin, E.; Roman, B.; Mejia, A. (August 1989), "Supernova 1989N in NGC 3646", IAU Circular, 4823: 2, Bibcode:1989IAUC.4823....2M
  6. ↑ Lopez, R.; Riera, A.; Cepa, J. (December 1989), "Supernova 1989N in NGC 3646", IAU Circular, 4932: 2, Bibcode:1989IAUC.4932....2L
  7. ↑ Johnson, Greg (18 August 1989), "Sophomore finds a bright spot in astronomy study", Los Angeles Times, retrieved 2023-07-27
  8. ↑ Garnavich, P.; Jha, S.; Kirshner, R.; Challis, P.; Berlind, P. (May 1999), "Supernova 1999cd in NGC 3646", IAU Circular, 7172: 1, Bibcode:1999IAUC.7172....1G
  9. ↑ Patat, F.; Rizzi, L.; Guzzo, L.; Guerrero, G. (May 1999), "Supernova 1999cd in NGC 3646", IAU Circular, 7172: 2, Bibcode:1999IAUC.7172....1G
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