NGC 3918

NGC 3918
A Hubble Space Telescope image of NGC 3918. Credit: ESA/Hubble and NASA.
Observation data (Epoch J2000.0)
Right ascension	11h 50m 17.7s[1]
Declination	-57° 10′ 56.9″[1]
Distance	4 900
Apparent magnitude (V)	8.5
Apparent dimensions (V)	8 to 10
Constellation	Centaurus
Physical characteristics
Other designations	He2-74 / Hen 2-74 / Sa2-81 / PK 294+4.1 / PN G294.6+04.7 / ESO 170-1[1]
See also: Planetary nebula, Lists of nebulae

NGC 3918 is a bright planetary nebula in the constellation Centaurus, that is called the "Blue Planetary" or "The Southerner". It is the brightest of the far southern planetary nebulae. This nebula was discovered by Sir John Herschel in March 1834, and is easily visible through small telescopes. The round or even slightly oval diameter is telescopically between 8 to 10 arcsec, though deep images extends this to about 19 or 20 arcsec. More surprising is the beautiful rich blue colour that looks much like the coloured images of Neptune taken by Voyager 2 in 1989.

Spectroscopy reveals NGC 3918 is approaching us at 17±3.0 kilometres per second, while the nebulosity is expanding at around 24 kilometres per second. The central star is 15.7B magnitude, and remains invisible to optical observers.

Distance is estimated 1.5 kpc.

References

1. ^ ^{a b c} "SIMBAD Astronomical Database". Results for NGC 3918. http://simbad.u-strasbg.fr/Simbad. Retrieved 2007-04-20. 

See also

• List of NGC objects
• List of planetary nebulae