IC 1318...

IC 1318, the Gamma Cygni nebula...

 

Objects: Gamma Cygni nebula (also designated as IC 1318, Sharpless 2-108) 
Type: Emission nebulae
Constellation: Cygnus
Distance: 4,500 light years
Equipment: Atik 460/EFW 2, Samyang 135mm lens@ F2, Vixen GPDX mount, guiding with Lodestar X2/PHD
Date: July 17th. 2021
Subframes: 12 x 300s for Ha, SII and OIII each, no flats, no darks (hot pixel removal in Astroart).

High overhead on summer evenings in the UK lies the Summer Triangle of bright stars comprising of Altair, Vega and Deneb. Deneb marks the tail of the celestial swan, Cygnus, through which runs the silvery streak of the Milky Way, down past Altair to the horizon. The area of Cygnus is particularly rich in star clouds, dark patches of interstellar dust and nebulae. One such area is clustered around the central star of the Northern Cross of Cygnus, and is called IC 1318.

Map showing field of image view... 

Discovered in August 1893 by Edward Barnard, IC 1318 is an emission nebula with an apparent size of 50 x 30 arc-min (or two full moons, side by side).

IC 1318 (Sh2-108) is commonly referred to as the “Gamma Cygni nebula” because of its apparent proximity to the F8Iab supergiant star (also called Sadr). γ Cygni is in fact a foreground object, lying 1,800 light-years from Earth. The nebula lies far beyond Gamma Cygni, in the depths of the Cygnus X complex of star formation regions some 4,500 light years away.

The nebulosity appears to contain a supernova remnant. Drake (1959) discovered a nebula about 3' southeast of γ Cygni in a pass-band centred near Ha. He also found that it was absent on a well-exposed blue-sensitive plate, and suggested that it is an H II region and not a reflection nebula. This “γ Cygni nebula” is buried in the photographic halation of the star so that it is not apparent on many plates such as the Palomar Sky Survey plate of the region, and it is not identical with an HII region 3° in diameter, S108 (Sharpless 1959), also called the “γ Cygni nebula.” Following Drake’s discovery, Mathewson, Large, and Haslam (1960), found a non-thermal radio source, or a component of confused sources, near the position of the small γ Cygni nebula, and they called it the “γ Cygni source.” It is the fourth-brightest supernova remnant at 400 MHz in the catalogue of Downes (D4, 1971). The nebula is also called DWB 63 and is the location of the radio source W66. According to Russian astronomer Veta Avedisova, DWB 63 is ionised by Gamma Cygni, the O8 V class HD 229202 and the B2 Ib supergiant HD 193946.

Avedisova also includes Sh 2-108 in star formation region SFR 78.18+1.82 along with infrared star cluster [BDB2003] G077.46+01.76 and numerous other nearby HII regions.

A band of dust runs across the region, appearing to divide part of the emission nebulosity in two and giving rise to the areas sometimes referred to as IC 1318A and IC1318B, also known as the “Butterfly Nebula”.

Tucked down at the bottom right-hand side of the above image can be seen the NGC 6888, the Crescent Nebula, which I have previously imaged in a much narrower field of view.

The above image is a blend of 1:1:1 RGB from Ha/SII/OIII narrowband data, with a starless (“Starnetted”) version with stars (20 x 15s each for RGB) added back in, to reduce the “starfog” caused by the background Milky Way.

References:

https://cseligman.com/text/atlas/ic13.htm

http://articles.adsabs.harvard.edu/pdf/1974ApJ...194..337J

http://galaxymap.org/cat/list/sharpless/101