Galaxy NGC 6951 + Integrated Flux Nebula

NGC 6951
NGC 6951: Galaxy in Cepheus; 500 mm Cassegrain 3625 mm f/7.2; SBIG STL11K; 490-150-150-150 min LRGB; Bernese Highlands; © 2019 Radek Chromik


In 1877 the French astronomer Jerome Eugene Coggia pointed the 7.2 inch f/11.5 comet finder refractor of the observatory in Marseille to the constellation Cepheus and discovered a nebula which he described as «fairly bright, oval, diffuse, star 15th magnitude east». Unfortunately he had gotten its position wrong by 20 arc minutes too far north. The following year, the American astronomer Lewis Swift encountered the same nebula with his 4.5 inch refractor, which he described as «fairly bright, fairly large, somewhat elongated» and whose position was correct measured The different positions led to John L. E. Dreyer listing Coggia's discovery as NGC 6952 and Swift's as NGC 6951 in his 1888 «New General Catalogue of Nebulae and Clusters of Stars» [313]. Already in the appendix of the first «Index Catalogue» [314], published in 1895, reference was made to the double entry following a reference by William Denning. In the appendix to the «Second Index Catalogue» [315] published in 1910, the position of NGC 6951 was stated to be correct and that NGC 6952 should be deleted. [196, 277]

Physical Properties

NGC 6951 is a Seyfert 2 galaxy with an active core and morphological type SAB(rs)bc. The distance is given as 16 to 24 Mpc. [145]

Long exposure images like Fig. 1 show nebulae that are in line of sight in front of the galaxy. These are large-scale gas and dust nebulae, so-called Integrated Flux Nebula (IFN), first discovered in 2005 by amateur astronomer Steve Mandel. Unlike the usual nebulae, these are located outside the plane of our Milky Way and are not illuminated by a single star, but by the sum of all stars in the Milky Way and shine very weakly. [271]

«Catalogue of Principal Galaxies (PGC)», Paturel et al. 1989 [144]
DesignationsPGC 65086: NGC 6951, NGC 6952, UGC 11604, MCG 11-25-2, CGCG 325-3, IRAS 20366+6555
Right Ascension (J2000.0)20h 37m 15.1s
Declination (J2000.0)+66° 06' 22"
Morphological TypeSB
Dimensions3.9' x 3.5'
Visual Magnitude11.8 mag
Radial Velocity (HRV)1425 km/s
Position Angle170°

Finder Chart

The galaxy NGC 6951 is located in the constellation of Cepheus. The best observation time is May to December.

Chart NGC 6951
Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]


144Catalogue of Principal Galaxies (PGC); Paturel G., Fouque P., Bottinelli L., Gouguenheim L.; Astron. Astrophys. Suppl. Ser. 80, 299 (1989); (2021-02-18)
145SIMBAD astronomical database;
149SkySafari 6 Pro, Simulation Curriculum;
160The STScI Digitized Sky Survey;
196Celestial Atlas by Curtney Seligman; (2020-12-28)
271«The Unexplored Nebula Project» Steve Mandel; (2021-12-25)
277«Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; (2021-02-17)
313«A New General Catalogue of Nebulae and Clusters of Stars, being the Catalogue of the late Sir John F.W. Herschel, Bart., revised, corrected, and enlarged» Dreyer, J. L. E. (1888); Memoirs of the Royal Astronomical Society. 49: 1–237; Bibcode:1888MmRAS..49....1D
314«Index Catalogue of Nebulæ found in the years 1888 to 1894, with Notes and Corrections to the New General Catalogue» Dreyer, J. L. E.; Memoirs of the Royal Astronomical Society, Vol. 51, p.185; 1895; Bibcode:1895MmRAS..51..185D
315«Second Index Catalogue of Nebulae and Clusters of Stars; containing objects found in the years 1895 to 1907, with Notes and Corrections to the New General Catalogue and to the Index Catalogue for 1888–94» Dreyer, J. L. E. (1910); Memoirs of the Royal Astronomical Society. 59: 105–198; Bibcode:1910MmRAS..59..105D