NGC 6946

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NGC 6946
NGC 6946.jpg
Spiral galaxy NGC 6946
Observation data (J2000 epoch)
Constellation Cepheus & Cygnus
Right ascension 20h 34m 52.3s[1]
Declination +60° 09′ 14″[1]
Redshift 0.000160[1]
Helio radial velocity 48 ± 2 km/s[1]
Distance 22.5 ± 7.8 Mly
(6.9 ± 2.4 Mpc)[2]
Apparent magnitude (V) +9.6[1]
Characteristics
Type SAB(rs)cd[1]
Apparent size (V) 11.5 x 9.8 arcmin[1]
Other designations
UGC 11597, PGC 65001, Arp 29,[1] Caldwell 12
See also: Galaxy, List of galaxies

NGC 6946 (also tentatively known as the Fireworks Galaxy) is an intermediate spiral galaxy about 22 million light-years away,[3] in the constellations of Cepheus and Cygnus. In the Catalogue of Named Galaxies, it is called 'Pyrobolus Cygni', or the "Fireworks Galaxy", because of the record number of supernovae discovered in it.[4] It was discovered by William Herschel on 9 September 1798. NGC 6946 is highly obscured by interstellar matter of the Milky Way galaxy, as it is quite close to the galactic plane. The true diameter of the galaxy is approximately 40,000 light-years or just about one-third of the Milky Way's size.[5] In the past century, ten supernovae have been observed to explode in the arms of this galaxy, which has been classified as a starburst galaxy. Chandra Space Telescope observations have, in fact, revealed three of the oldest supernovae ever detected in X-rays, giving more credence to its nickname. This composite image also includes optical data from the Gemini Observatory in red, yellow, and cyan.[6]

Supernovae[edit]

Ten supernovae have been observed in NGC 6946 in the last 100 years: SN 1917A, SN 1939C, SN 1948B, SN 1968D, SN 1969P, SN 1980K, SN 2002hh, SN 2004et, SN 2008S, and SN 2017eaw.[7][8][9] This makes it the most prolific known galaxy for this type of event over a period of 100 years. By comparison, the Milky Way galaxy, which has double the number of stars as NGC 6946, averages one supernova event per century.[10] It also contains a failed supernova, potential black hole-forming star N6946-BH1.[11]

References[edit]

  1. ^ a b c d e f g h "NASA/IPAC Extragalactic Database". Results for NGC 6946. Retrieved 2006-11-18. 
  2. ^ "Distance Results for NGC 6946". NASA/IPAC Extragalactic Database. Retrieved 2010-06-18. 
  3. ^ Boen, Brooke (20 May 2015). "NGC 6946: The 'Fireworks Galaxy'". NASA. Retrieved 2016-12-08. 
  4. ^ Bodifee, Gerard. "Catalogue of One Thousand Named Galaxies" (PDF). Retrieved 21 May 2017. 
  5. ^ Nemiroff, R.; Bonnell, J., eds. (1 January 2011). "Fireworks Galaxy NGC 6946". Astronomy Picture of the Day. NASA. 
  6. ^ [1]
  7. ^ http://www.astronomerstelegram.org/?read=10372
  8. ^ http://www.astronomerstelegram.org/?read=10376
  9. ^ "List of Supernovae". Harvard-Smithsonian Center for Astrophysics (IAU). Retrieved 2010-07-12. 
  10. ^ "Gemini Observatory Welcomes 2005 with Release of Galactic Fireworks Image", Gemini Observatory, 1 January 2005, retrieved 2016-01-04. 
  11. ^ Adams, S. M.; Kochanek, C. S.; Gerke, J. R.; Stanek, K. Z.; Dai, X. (9 September 2016). "The search for failed supernovae with the Large Binocular Telescope: conformation of a disappearing star". arXiv:1609.01283v1Freely accessible. 

External links[edit]

Coordinates: Sky map 20h 34m 52.3s, +60° 09′ 14″