Blue Planetary (NGC 3918)
A small, bright planetary nebula in Centaurus that shows blue in a telescope. Its Gaia parallax is too uncertain to use, so its distance is a statistical estimate between about 4,200 and 6,400 light-years.
Planetary nebula in Centaurus. Magnitude 8.1.
Can you see it from Guyana?
From Georgetown (6.8° N) it climbs to 26° above the southern horizon at its highest; from Lethem (3.4° N), to 29° above the southern horizon. It is highest at midnight on the night of 17 Mar, in the middle of its season. The page works out tonight's rise, highest point and set for both towns in Guyana time (UTC-4), and where the Moon is.
What you'll see
- Your eyes: Not visible to the eye. It lies 3.6° north-west of Imai.
- 10x50 binoculars: Looks like a faint star; it needs a telescope.
- A small telescope (80 to 100 mm): A small, bright blue disc at 100x or more, like an out-of-focus star.
- A camera: Tiny on camera: it needs 2,000 mm or more of focal length on a tracking mount.
How big, how bright, how far
- Size on the sky: 19″, 1/98 of the Moon's width (the Moon is about 31′ wide).
- Brightness: magnitude 8.1. Fainter than the faintest stars in Georgetown (4.3) and Lethem (6.0): binoculars or a telescope.
- Distance: 5,000 light-years. The light reaching your eye left it about 5,000 years ago.
- True size: 0.49 light-years across its catalogued outline; light crosses it in 6 months.
Apparent size from OpenNGC (Mattia Verga), CC-BY-SA-4.0.
What it is made of
- Type
- Planetary nebula
What is in it, not measured:
- Ionised gas: thrown off by a dying star: hydrogen, helium, oxygen, nitrogen
- The hot exposed core: becoming a white dwarf
How we know: Distance from a statistical distance from how bright its surface is for its size (its Gaia parallax has a 33% error): Stanghellini & Haywood 2010, ApJ 714, 1096 (2010ApJ...714.1096S, via SIMBAD mesDistance): 1.623 ± 0.324 kpc. True size: the apparent size times the distance (apparent size: OpenNGC (Mattia Verga, CC BY-SA 4.0), commit 4e2398a2).
More deep-sky objects: Statue of Liberty Nebula (NGC 3576) · Coalsack Nebula · Eight-Burst Nebula (NGC 3132) · Ghost of Jupiter (NGC 3242) · Bug Nebula (NGC 6302) · Cat's Paw Nebula (NGC 6334)