NGC 3918
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| NGC 3918 | |
 A Hubble Space Telescope (HST) image of NGC 3918. Credit: HST/NASA/ESA. |
|
| 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 nebula NGC 3918 was discovered by Sir John Herschel in March 1834, and in easily visible in a small telescope. 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.
