A Hubble Space Telescope image of NGC 3918.
Credit: ESA/Hubble and NASA.
|Right ascension||11h 50m 17.7s|
|Declination||−57° 10′ 56.9″|
|Apparent magnitude (V)||8.5|
|Apparent dimensions (V)||8 to 10|
He2-74 / Hen 2-74 / Sa2-81 / PK 294+4.1 / PN G294.6+04.7 /
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 14.6 visible light magnitude, and remains invisible to optical observers, as it is obscured by the sheer brightness of the surrounding nebula.
Distance is estimated 1.5 kpc.