NGC 6946

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Galaxy
NGC 6946
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Photo from the Schulman Telescope at the Mount Lemmon SkyCenter
Photo from the Schulman Telescope at the Mount Lemmon SkyCenter
AladinLite
Constellation Cepheus
Position
equinox :  J2000.0 , epoch : J2000.0
Right ascension 20 h 34 m 52.3 s
declination + 60 ° 09 ′ 14 ″
Appearance
Morphological type SAB (rs) cd / Sy2 / HII  
Brightness  (visual) 9.0 mag
Brightness  (B-band) 9.7 likes
Angular expansion 11.5 ′ × 9.8 ′
Position angle 57 °
Surface brightness 14.0 mag / arcmin²
Physical data
Redshift 0.000133 ± 0.000007  
Radial velocity (+40 ± 2) km / s  
Stroke distance
v rad  / H 0 		(12 ± 1)  x  10 6  ly
(3.65 ± 0.29)  Mpc 
history
discovery FW Herschel
Discovery date September 9, 1798
Catalog names
NGC  6946 • UGC  11597 • PGC  65001 • CGCG  304-6 • MCG  + 10-29-6 • IRAS  20338 + 5958 • Arp  29 • GC  4594 • H  IV-76 • h  2084 •

NGC 6946 = Arp 29 or fireworks galaxy is a bar-spiral galaxy of the Hubble type SAB (rs) cd in the constellation Cepheus on the border with the constellation Cygnus in the northern sky . It has an angular dimension of 11.5 '× 9.8' and an apparent magnitude of 9.0 mag.

The galaxy is close to our galactic plane, so the light that comes to us from NGC 6946 is heavily darkened by gas and dust from our galaxy . This makes it difficult to observe this galaxy and its members and, in particular, to determine their distance. In particular, their distance should be determined from the supernova observations, for which, in addition to the apparent brightness and the absolute brightness , the interstellar extinction (in this case difficult to measure) must be known. A calculation published in 1997 showed a photometric distance of 6.4 megaparsecs (21 million light years ). Other measurements gave values ​​between 4.1 and 10.5 megaparsecs. NGC 6946 tops the statistics of supernova frequencies over the past hundred years with a number of ten.

Halton Arp organized his catalog of unusual galaxies into groups according to purely morphological criteria. This galaxy belongs to the class spiral galaxies with a pronounced arm ( Arp catalog ).

The object was discovered on September 9, 1798 by the German-British astronomer Friedrich Wilhelm Herschel .

Web links

literature

  • Jeff Kanipe and Dennis Webb: The Arp Atlas of Peculiar Galaxies - A Chronicle and Observer's Guide , Richmond 2006, ISBN 978-0-943396-76-7

Individual evidence

  1. ↑ a b c d NASA / IPAC EXTRAGALACTIC DATABASE
  2. ↑ a b c d e SEDS : NGC 6946
  3. ↑ Photometric distance ( ME Sharina et al .: Photometric Distance of the Galaxy NGC 6946. )
  4. ↑ Quoted from Bonnarel, F., Boulesteix, J., & Marcelin, M .: Morphology of the ionized gas in the spiral galaxy NGC 6946
  5. ↑ Seligman