Fetus Nebula (NGC 7008)

NGC 7008
NGC 7008: Fetus Nebula in Cygnus; 500 mm Cassegrain 3625 mm f/7.2; SBIG STL11K; 100+3*30 min LRGB; Bernese Highlands; © 2011 Radek Chromik [32]

History

This nebula was discovered by William Herschel on 14 October 1787 and cataloged as I 192 with the description: «Considerably bright of irregular figure, 3' long, 2.5' broad nebulosity.» [464] In 1888 John L. E. Dreyer cataloged it as NGC 7008 in his «New General Catalogue». [313]

Between 1911 to 1916 the American astronomer Francis G. Pease took a picture with the 60 inch f/5 reflector on Mount Wilson and recognized the nature of NGC 7008 as a planetary nebula. He described the picture as follows: «This planetary nebula is elliptical in shape, 95"x75", p=5°, containing much detail. The strongest bits of nebulosity are two condensations just E of the N end of the major axis. On the south following side the elliptical form seems eaten away, but traces of nebulosity may be seen connecting with a star which lies p=156°. A number of stars a magnitude or two fainter than the nucleus appear in the nebula. Except for one, they are surrounded by a dark ring which un turn opens directly on a dark region. As the nucleus itself presents this appearance, it is suggested that these stars lie within the nebula. One of the stars, p=240°, 23", appears elongated; it may be a double star or a very bright bit of nebulosity. One star at p=65°, 29", with respect to the nucleus, is but partly surrounded by the dark ring. Huggins found the spectrum to be gaseous.» [601]

Physical Properties

NGC 7008 is the shed shell of a red giant that has used up all its hydrogen and has evolved into a white dwarf in the final stage. The apparent magnitudes of the nebula measured with different filters are: R 13.2 mag, J 11.8 mag, H 11.5 mag, K 11.4 mag. The distance from Earth is 869 parsecs, around 2800 light years. [145]

South of NGC 7008 is another binary star system. The main star HD 235422 of spectral type K7 has an apparent visual magnitude of 9.5 mag and its companion HJ 1606 appears 11.6 mag bright. The two 18.7 arc seconds separated stars are at a distance of 469 parsecs, about 1500 light-years and are therefore unrelated to the planetary nebula. [145]

«Strasbourg-ESO Catalogue of Galactic Planetary Nebulae» Acker et al., 1992 [141]
Designations PN G093.4+05.4: NGC 7008, PK 93+05.2, ARO 39, VV 258, VV' 540
Right Ascension (J2000.0) 21h 00m 33s
Declination (J2000.0) +54° 32' 29"
Dimensions 86." (optical), 95." (radio)
Distance 1.3 kpc
Radial Velocity -74.2 ± 2.0 km/s
Expansion Velocity 40.0 (O-III) km/s
C-Star Designations AG82 417, CSI +54 -20591, GCRV 13203, PLX 5049
C-Star Magnitude U: 12.99, B: 13.75, V: 13.23
C-Star Spectral Type O7, O(H)
Discoverer PEASE 1917

Finder Chart

The planetary nebula NGC 7008 is located in the constellation Cygnus. The best observing time is April to November, when the PN is highest in the night sky.

Finder Chart Fetus Nebula (NGC 7008)
Fetus Nebula (NGC 7008) in constellation Cygnus. Charts created using SkySafari 6 Pro and STScI Digitized Sky Survey. Limiting magnitudes: Constellation chart ~6.5 mag, DSS2 close-ups ~20 mag. [149, 160]

Objects Within a Radius of 15°

References