NGC 691

NGC 691 is an unbarred spiral galaxy located in the constellation Aries. It is located at a distance of circa 120 million light years from Earth, which, given its apparent dimensions, means that NGC 691 is about 130,000 light years across. It was discovered by William Herschel on November 13, 1786.[3]

NGC 691
NGC 691 by the Liverpool Telescope
Credit: Göran Nilsson & The Liverpool Telescope
Observation data (J2000 epoch)
ConstellationAries
Right ascension01h 50m 41.7s[1]
Declination+21° 45′ 36″[1]
Redshift0.008889 ± 0.000013 [1]
Helio radial velocity2,665 ± 5 km/s[1]
Distance119 ± 14 Mly (36.5 ± 4.3 Mpc)[1]
Apparent magnitude (V)11.5 [2]
Characteristics
TypeSA(rs)bc [1]
Apparent size (V)3′.5 × 2′.6 [1]
Other designations
UGC 1305, CGCG 482-023, MCG +04-05-019, PGC 6793[1]

NGC 691 features a multiple ring structure, with three rings recognised in the infrared, with diameters of 1.03, 1.67, and 2.79 arcminutes.[4] When imaged in H-alpha, the galaxy appears patchy. The total star formation rate of the galaxy is estimated to be about 0.6 M☉ per year.[5] One supernova has been observed in NGC 691, SN 2005W. It was discovered by Yoji Hirose in unfiltered CCD frames taken on Feb. 1.442 UT with a 0.35-m f/6.8 Schmidt-Cassegrain reflector. The supernova was located 56" east and 1" south of the center of NGC 691 and at the time of the discovery had an apparent magnitude of 15.2.[6] Spectrographic observations indicated it was a type Ia supernova about a week before maximum.[7] The peak magnitude of the supernova was 14.3, on February 10.759.[8]

NGC 691 is the foremost member of a galaxy group known as the NGC 691 group. Other members of the group include IC 163, NGC 678, NGC 680, NGC 694, IC 167, and NGC 697.[9]

References
  1. "NASA/IPAC Extragalactic Database". Results for NGC 691. Retrieved 2016-01-18.
  2. "Revised NGC Data for NGC 691". spider.seds.org. Retrieved 25 November 2018.
  3. Seligman, Courtney. "NGC 691 (= PGC 6793)". Celestial Atlas. Retrieved 19 November 2018.
  4. Comerón, S.; Salo, H.; Laurikainen, E.; Knapen, J. H.; Buta, R. J.; Herrera-Endoqui, M.; Laine, J.; Holwerda, B. W.; Sheth, K.; Regan, M. W.; Hinz, J. L.; Muñoz-Mateos, J. C.; Gil de Paz, A.; Menéndez-Delmestre, K.; Seibert, M.; Mizusawa, T.; Kim, T.; Erroz-Ferrer, S.; Gadotti, D. A.; Athanassoula, E.; Bosma, A.; Ho, L. C. (19 February 2014). "ARRAKIS: atlas of resonance rings as known in the S4G". Astronomy & Astrophysics. 562: A121. arXiv:1312.0866. Bibcode:2014A&A...562A.121C. doi:10.1051/0004-6361/201321633. S2CID 119295831.
  5. Erroz-Ferrer, Santiago; Knapen, Johan H.; Leaman, Ryan; Cisternas, Mauricio; Font, Joan; Beckman, John E.; Sheth, Kartik; Muñoz-Mateos, Juan Carlos; Díaz-García, Simón; Bosma, Albert; Athanassoula, E.; Elmegreen, Bruce G.; Ho, Luis C.; Kim, Taehyun; Laurikainen, Eija; Martinez-Valpuesta, Inma; Meidt, Sharon E.; Salo, Heikki (21 July 2015). "Hα kinematics of S4G spiral galaxies – II. Data description and non-circular motions". Monthly Notices of the Royal Astronomical Society. 451 (1): 1004–1024. arXiv:1504.06282. Bibcode:2015MNRAS.451.1004E. doi:10.1093/mnras/stv924. S2CID 73618748.
  6. "IAUC 8475: 2005W; 2005U; C/2004 Y9-Y11, C/2005 B2". www.cbat.eps.harvard.edu. IAU. 2 February 2005.
  7. "IAUC 8479: 2005ab, 2005ad; 2005W; C/1995 O1; N IN M31". www.cbat.eps.harvard.edu. IAU. 7 February 2005.
  8. "IAUC 8486: 2005ah; 2005ai; 2004gw, 2005T,, 2005ae; 2005W". www.cbat.eps.harvard.edu. IAU. 13 February 2005.
  9. Garcia, A. M. (1993). "General study of group membership. II - Determination of nearby groups". Astronomy and Astrophysics Supplement Series. 100 (1): 47–90. Bibcode:1993A&AS..100...47G. ISSN 0365-0138.
  • Media related to NGC 691 at Wikimedia Commons


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